Switched from CM3000 to CAX80 and it destroyed upload/download speeds

[goobledegook]

So I recently moved to Benicia, CA and signed up for the 2Gbps download 300Mbps upload package Xfinity offers. At first I got the CM3000 just missing the fact that it only supported 1Gbps but ran a speed test and got what I was expecting (941Mbps down and 358Mbps up). I decided to get the CAX80 since it has the 2.5Gbps port and I wanted the Wifi. So I replaced the the CM3000 with the CAX80, registered it with Xfinity, went through the set up process using the Nighthawk app and now I'm getting worse speeds (700Mbps down, and 5.88Mbps up). I haven't changed my set up in any way other than doing this. What's going on?

So to reiterate (ran these tests multiple times on both modems):

CM3000: 941Mbps down and 358Mbps up
CAX80: 700Mbps down (1.34x slower) and 5.88Mbps up (60x slower!)

CAX80 Firmware Version: V5.1.1.8
CAX80 Cable Firmware Version V1.02.08

OS: Windows 11

Any suggestions/ideas? Been searching but any related posts are old.

Downstream Status: Poor

Downstream Power Level: Poor
Downstream power is poor (10.3dBmV). The recommended level is between -10dBmV to 10dBmV.

Downstream SNR: Good

Upstream Status: Good

Upstream Power Level: Good

Current time: Thu Jan 09 00:24:35 2025

Startup Procedure
Acquire Downstream Channel: 639 MHz Locked
Connectivity State: OK Operational
Boot State: OK Operational
Security: Enabled BPI+

Downstream Bonded Channels
Channel LockedStatus Modulation ChannelID Frequency Power SNR Correctables Uncorrectables
1 Locked 256 QAM 44 639000000 Hz 10.3 dBmV 44.2 dB 0 0
2 Locked 256 QAM 13 453000000 Hz 7.5 dBmV 43.7 dB 0 0
3 Locked 256 QAM 14 459000000 Hz 7.6 dBmV 43.7 dB 0 0
4 Locked 256 QAM 15 465000000 Hz 7.7 dBmV 43.7 dB 0 0
5 Locked 256 QAM 16 471000000 Hz 7.9 dBmV 43.9 dB 0 0
6 Locked 256 QAM 17 477000000 Hz 8 dBmV 43.9 dB 0 0
7 Locked 256 QAM 18 483000000 Hz 8 dBmV 43.9 dB 0 0
8 Locked 256 QAM 19 489000000 Hz 8.2 dBmV 44 dB 0 0
9 Locked 256 QAM 20 495000000 Hz 8.2 dBmV 44.1 dB 0 0
10 Locked 256 QAM 21 501000000 Hz 8.3 dBmV 44.1 dB 0 0
11 Locked 256 QAM 22 507000000 Hz 8.6 dBmV 44.2 dB 0 0
12 Locked 256 QAM 23 513000000 Hz 8.5 dBmV 44.2 dB 0 0
13 Locked 256 QAM 24 519000000 Hz 8.7 dBmV 44.3 dB 0 0
14 Locked 256 QAM 25 525000000 Hz 8.7 dBmV 44.3 dB 0 0
15 Locked 256 QAM 26 531000000 Hz 8.8 dBmV 44.3 dB 0 0
16 Locked 256 QAM 27 537000000 Hz 8.8 dBmV 44.3 dB 0 0
17 Locked 256 QAM 28 543000000 Hz 8.7 dBmV 44.2 dB 0 0
18 Locked 256 QAM 29 549000000 Hz 8.7 dBmV 44.2 dB 0 0
19 Locked 256 QAM 30 555000000 Hz 8.9 dBmV 44.3 dB 0 0
20 Locked 256 QAM 31 561000000 Hz 8.9 dBmV 44.3 dB 0 0
21 Locked 256 QAM 32 567000000 Hz 9 dBmV 44.3 dB 0 0
22 Locked 256 QAM 33 573000000 Hz 9.1 dBmV 44.4 dB 0 0
23 Locked 256 QAM 34 579000000 Hz 9.2 dBmV 44.4 dB 0 0
24 Locked 256 QAM 35 585000000 Hz 9.3 dBmV 44.4 dB 0 0
25 Locked 256 QAM 36 591000000 Hz 9.3 dBmV 44.4 dB 0 0
26 Locked 256 QAM 37 597000000 Hz 9.4 dBmV 44.4 dB 0 0
27 Locked 256 QAM 38 603000000 Hz 9.6 dBmV 44.5 dB 0 0
28 Locked 256 QAM 39 609000000 Hz 9.5 dBmV 44.3 dB 0 0
29 Locked 256 QAM 40 615000000 Hz 9.6 dBmV 44.3 dB 0 0
30 Locked 256 QAM 41 621000000 Hz 9.9 dBmV 44.4 dB 0 0
31 Locked 256 QAM 42 627000000 Hz 9.9 dBmV 44.4 dB 0 0
32 Locked 256 QAM 43 633000000 Hz 10.2 dBmV 44.5 dB 0 0

Upstream Bonded Channels
Channel LockedStatus ChannelType ChannelID SymbolRate Frequency Power
1 Locked ATDMA 19 5120 Ksym/sec 29200000 Hz 42.0 dBmV
2 Locked ATDMA 18 5120 Ksym/sec 22800000 Hz 42.0 dBmV
3 Locked ATDMA 17 5120 Ksym/sec 16400000 Hz 41.5 dBmV
4 Locked ATDMA 20 5120 Ksym/sec 35600000 Hz 42.3 dBmV
5 Not Locked Unknown 0 0 0 0.0
6 Not Locked Unknown 0 0 0 0.0
7 Not Locked Unknown 0 0 0 0.0
8 Not Locked Unknown 0 0 0 0.0

Downstream OFDM Channels
Channel LockedStatus ProfileID ChannelID Frequency Power SNR/MER ActiveSubcarrier Unerror Correctable Uncorrectable
1 Locked 0 ,1 ,2 ,3 193 722000000 Hz 12.58 dBmV 45.1 dB 388 ~ 3707 397620190 110024534 0
2 Locked 0 ,1 ,2 ,3 194 957000000 Hz 16.18 dBmV 45.3 dB 148 ~ 3947 405019767 4324629 0

Upstream OFDMA Channels
Channel LockedStatus ProfileID ChannelID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV

Event Log
Time Priority Description
Wed Jan 8 23:50:08 2025 Notice CM-STATUS message sent. Event Type Code: 24; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 23:43:25 2025 Notice CM-STATUS message sent. Event Type Code: 16; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 21:42:38 2025 Notice CM-STATUS message sent. Event Type Code: 24; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 21:38:17 2025 Notice CM-STATUS message sent. Event Type Code: 16; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 20:33:41 2025 Notice CM-STATUS message sent. Event Type Code: 24; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 20:29:14 2025 Notice CM-STATUS message sent. Event Type Code: 16; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 20:28:53 2025 Notice CM-STATUS message sent. Event Type Code: 24; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 20:26:47 2025 Notice CM-STATUS message sent. Event Type Code: 16; Chan ID: 193; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 19:37:12 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 19:37:12 2025 Notice DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 19:37:10 2025 Notice DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 19:37:09 2025 Notice TLV-11 - unrecognized OID;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:29 1970 Notice Honoring MDD; IP provisioning mode = IPv6
Thu Jan 1 00:00:22 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:21 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 19:28:40 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:30 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:29 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 18:04:30 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:26 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:25 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 17:44:16 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:45 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:43 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 17:42:03 2025 Critical Resetting the cable modem due to docsDevResetNow
Wed Jan 8 17:35:05 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:46 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:43 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 17:29:18 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:45 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:43 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Wed Jan 8 17:26:23 2025 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:03:15 1970 Critical No Ranging Response received - T3 time-out;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:03:12 1970 Critical UCD invalid or channel unusable;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:90:f0:1c:02:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:02:53 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
Thu Jan 1 00:00:46 1970 Critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=54:07:7d:c3:7a:00;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

[goobledegook]

Just wanted to post this here as well as the CAX80 is recommended for 2Gbps download (although curiously doesn't not list upload speed).

https://assets.xfinity.com/assets/dotcom/projects/cix-4997_compatible-devices/2023.11.22%20Full%20Li...

[FURRYe38]

Power levels are too high:

https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router

Find you a -6Db coax attenuator.

Any Criticals, Errors or Warnings seen in the event logs needs to be reviewed and resolved by the ISP. Indicates a signal issue on the ISP line up to the modem.

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html
https://highspeed.tips/docsis-events/

[plemans]

You sure you have the CM3000? It supports multigig and the increased upload from xfinity. The cax80 doesn't have the next gen upload speeds. 

[goobledegook]

Also, firmware version was posted in the OP.

[FURRYe38]

The CAX80 is a solid gateway, if and when the modem signals are with in spec. If they are not then those need to be addressed first. 

All support and information is between NG and the ISP regarding modem side support and information. Nothing else can be done from the forums. I'ts all up to the ISP to test and certify FW that comes from NG. 

[goobledegook]

I appreciate the reply, however, CM3000 works "ok" as in great upload speed, but not getting the full 2Gbps download speed. Ran it against several servers close to me and it seems consistent no matter time of day or day of week.

My main issue is with the CAX80 which I'm returning. Using the same cables (other than the power adapter of course, hehe, I'm of course using the one that came with the CAX80), I'm getting 60x slower upload speeds while slower download speeds than the CM3000. I can understand the coax needing an attenuator, but that would not explain just getting 5Mbps upload compared to 400Mbps+ consistently since it's obviously capable of downloading at a much higher speed (~700Mbps, which is a lot lower than the CM3000 since I'm on a 2Gbps line, although I'm "only" getting 1.2Gbps on the CM3000).

For these reasons I'm returning the CAX80. I have asked Xfinity to send me a rental modem/router combo to see if I'm getting the speeds that my plan is supposed to give me and if it does, I'll return the CM3000 as well.

Appreciate your attempt to help tho.

[jay_w]

I have a few more suggestions, I’ll write them down when I’m back at the house in a few hours. I spent weeks tinkering with my setup, different splitters, etc.

But in the meanwhile what WiFi router are you using with the CM3000?

I ask because the CM3000 is the best on the market that I know of, and I am getting 2gb all the way through to the router with the same modem.

[goobledegook]

That would be great, thank you. To answer your question, just temporarily I'm using a switch (Nicgiga S100-0800T) while testing just to make sure there's no interference from the router.

[FURRYe38]

I'd post the cable connections data page and the event log from the CM modem while you have it connected. It does support 2Gb on the download and over 200Mbps on the up I believe now with those ISPs that support it. So the CM should be working. However if there are issues on the ISP coax line, this will be a cause of problems. 

---

@goobledegook wrote:

I appreciate the reply, however, CM3000 works "ok" as in great upload speed, but not getting the full 2Gbps download speed. Ran it against several servers close to me and it seems consistent no matter time of day or day of week.

My main issue is with the CAX80 which I'm returning. Using the same cables (other than the power adapter of course, hehe, I'm of course using the one that came with the CAX80), I'm getting 60x slower upload speeds while slower download speeds than the CM3000. I can understand the coax needing an attenuator, but that would not explain just getting 5Mbps upload compared to 400Mbps+ consistently since it's obviously capable of downloading at a much higher speed (~700Mbps, which is a lot lower than the CM3000 since I'm on a 2Gbps line, although I'm "only" getting 1.2Gbps on the CM3000).

For these reasons I'm returning the CAX80. I have asked Xfinity to send me a rental modem/router combo to see if I'm getting the speeds that my plan is supposed to give me and if it does, I'll return the CM3000 as well.

Appreciate your attempt to help tho.

---

[jay_w]

Looking at your logs. You have quite a few errors there, but I go through periods of high errors and then sometimes weeks without a single error. This is almost always the Xfinity side but their support script is to blame the customer and tell them they need Xfinity hardware… which I think probably just hides the errors

Either way, let’s make sure we didn’t miss a bottleneck.

I’m assuming since you’re using a switch, you must be testing over a cable through a PC.

The uplink port on the switch is 2.5 or better I hope? You can also check the actual uplink connection speed through the switch if it has a managed UI. Otherwise this would bottleneck your connection.

Also, you should be using a CAT 6 or better cable. If not a shielded cable ensure there are no power cords crossed over the cable.

Also your switch should be at least 6 inches away from the modem to rule out EM interference.

If you’re not sure, then you can also try to plug directly into the back of the modem from your PC.

Next. Your PC should have a multi-gig connection to the switch. The standard is 1gb assuming your PC has 10gb?

The focus would be your COAX coming in from Xfinity. As others have mentioned downstream signal power should be between -10 and +10.

Your numbers are not horrible, only slightly out of spec. For my numbers, I landed on 7.x dbmv power download with 44 db SNR… and then 4 channels locked for upload with 41 dbmv power.

Xfinity lines are usually a little hot 9-12 dbmv coming from the street junction. Because they anticipate you will have 1 or 2 splitters.

My setup looks like this > Xfinity cable > MOCA filter > 2 way Amphenol splitter. Then from the splitter, I have one cable going to the modem without any attenuators. The other is capped with a terminator

This splitter only reduces my power by 3.7db. I did this by design because the house has 3 cable lines running to rooms. These lines are not used because we stream everything so I disconnected them to reduce any back feeding of interference. If I choose to use them, I can use a second splitter off the first one with plenty of power left.

Alternatively I could have used a 3 way or 4 way splitter and reduced my power by 5.8 or 7.3db.

Since your upload power is good, I would not use an attenuator. I ran into to a problem with correctables when I did that. Instead I would focus on your splitters and signal quality..

What does your coax setup look like? How many splitters? Where is the MOCA filter? Are they very old?

[goobledegook]

Thanks for the extensive list! Overall I'm happy with the CM3000, my reason for posting was because of the performance of the CAX80 that I wanted to try out since it's a Modem/Router/Wifi combo so I didn't have to use a separate router.

However, just some quick answers:

• Cables I'm using are all CAT6 or CAT6e. I haven't but I'll make sure they aren't crossing over any power chords.
• Switch supports 10Gbase-T, 5GbE, 2.5GbE, and 1GbE speeds (Nicgiga S100-0800T)
• Switch is over 6 inches away
  • And yep, tried going straight into my PC so the Switch wasn't a factor. I'll be doing this by default right now just to minimize any problems that doesn't have to do with either the CM3000 or if I try out the CAX80 again.
• My network port on my PC(s) are 10Gb yeah.
• No COAX splitter, all I'm using the COAX port is for the modem, nothing else. I did get an attenuator to try with the CAX80 like @FURRYe38 recommended.

I got the 2Gbps plan mostly for the 400Mbps upload speed since I'm a game developer and work remotely from home. We run Perforce if you know what that is (where the game is "housed") so it really helps to have a higher upload speed when submitting assets.

I'll probably will still send back the CAX80 and just get a good router and use that with the CM3000 and my switch.Thanks for all the help!

[jay_w]

Good luck. A few final thoughts. So the 80 with the 2.5 port configured to the switch should support 2gb down, but I don’t think the 80 has mid-split support for upload… Does it?

As you know, upload is helpful for video conferencing and little helpful for gaming (to have more upload bandwidth). So assuming the 80 doesn’t have mid-split, nothing will fix that. It’s just not supported.

[goobledegook]

I don't think you fully read my e-mails, upload is important for my work, but I do appreciate your responses! I did not know the CAX80's lack of a mid-split would tank the upload to 5Mbps, I'll definitely be sending it back.

Thank you.

[FURRYe38]

Since the power is out of spec and your seeing Criticals when you had the CAX80 online:

Downstream Status: Poor

Downstream Power Level: Poor

This means the CAX80 is not getting good ISP signal on the line. Power is TOO HIGH and any criticals, errors or warnings in the event logs means there is signal issues on the ISP coax line. Too high power will eventually burn out the modem. So the CAX80 will not be working as designed. Also since you have the CM modem online now, the CM modem maybe seeing same issues. 

All these would cause problem and lead to what your seeing. 

Hope your CM3000 won't see problems. 

Good Luck.