C6220 Frequent Wifi disconnects and/or modem crashes

[SJH13]

Issue:  Modem/Router goes offline frequently from twice a day to twice a week. 

Firmware on the Modem/Router V1.02.11.   

Xfinity Service package: Internet only, Performance Select  100mbs

The cable enters the house from outside and is directly connected to the Netgear C6220, no splitters.

No computer at the house.  I have set up remote access on the modem/router and am accessing it from a different location.

There are only 6 devices connected to wifi:  they are all "smart" sensors that run on the 2.4ghz band.  Nothing is running on the 5g band, unless I go to the property and connect my phone to 5g. 

When I connect to 5g, the speed is as expected.

I know when the modem/router goes down, because all my devices alert me via text & email, with a time stamp.

The time stamp of when they go down does not always match the timestamp in the logs on the modem/router.

I have remote access enabled on the modem/router, and when it "goes down" I attempt to access it via my computer, and am unable to do so until I  log into my Xfinity.com account, and reboot the modem from the Xfinity interface. 

I have never been at the property when it goes down, and so have not looked at the lights on the modem/router.

This is what I've done, in my attempts to fix this issue:

1)  Unplugged the modem for 20 minutes, then plugged it back in and rebooted.

2)  Cleaned the contacts and tightened them.

3)  Tested the wifi using Ookla, M-Lab and Xfinity speed test

(at 6 feet away on the 2.4 band, it's fluctuates between 10 and 40 mbps download and 1 to 15 upload)

4)  Tested the modem with a direct RJ45 connection (Download over 121, which is fine, I'm only paying for 100, upload is adaquate)

5)  Changed the 2.4 channel to 11 (had less traffic), now it's got a lot of traffic, so I'm changing it to "auto"

6)  Moved the modem to a position where it had more air circulating underneath it, as it seemed overly warm

I'm posting logs below.  Stangely the logs do not reflect the same time of failure as my devices do.  For example, all my devices went down on Feb 13, 2021 at 1:35 AM.  The log shows the Modem/Router going down at 7:48 AM, which is actually the time when I reset it.

Also, note the difference in todays (2/13/2021) cable log, and the last time it went down, on 2/8/2021, five days ago.

Thanks for any help anyone can give.

2021-02-13, 07:50:45.0	Warning (5)	MDD message timeout;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.1;CM-VER=3.0;
2021-02-13, 07:48:37.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-02-03, 17:12:39.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-02-03, 17:06:32.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-02-02, 08:56:58.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-02-02, 07:47:17.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-01-27, 10:43:58.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-01-21, 20:21:12.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-01-16, 16:04:55.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-01-11, 18:40:13.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-01-05, 14:55:40.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2021-01-05, 09:04:39.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2020-12-31, 08:07:39.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2020-12-28, 07:33:49.0	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.1;CM-VER=3.0;
2020-12-25, 11:12:53.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
2020-12-24, 19:32:21.0	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.1;CM-VER=3.0;
2020-12-19, 07:25:59.0	Critical (3)	Resetting the cable modem due to docsDevResetNow
Time Not Established	Notice (6)	Honoring MDD; IP provisioning mode = IPv6
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;
Time Not Established	Critical (3)	No Ranging Response received - T3 time-out;CM-MAC=28:80:88:9a:7e:30;CMTS-MAC=00:01:5c:66:00:46;CM-QOS=1.0;CM-VER=3.0;

Cable Log from today 2/13/2021

Frequency start Value
This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect.
Starting Frequency
Startup Procedure
Procedure Status Comment Acquire Downstream Channel 501000000 Hz Locked Connectivity State OK Operational Boot State OK Operational Configuration File OK Security Enable BPI+ IP Provisioning Mode Honor MDD IPv6 only
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked QAM256 16 501000000 Hz 11.2 dBmV 40.8 dB 0 0 2 Locked QAM256 17 507000000 Hz 11.3 dBmV 40.8 dB 0 0 3 Locked QAM256 18 513000000 Hz 11.2 dBmV 40.8 dB 0 0 4 Locked QAM256 19 519000000 Hz 11.1 dBmV 40.8 dB 0 0 5 Locked QAM256 20 525000000 Hz 11.1 dBmV 40.8 dB 0 0 6 Locked QAM256 21 531000000 Hz 11.3 dBmV 40.8 dB 0 0 7 Locked QAM256 22 537000000 Hz 11.3 dBmV 40.9 dB 0 0 8 Locked QAM256 23 543000000 Hz 11.2 dBmV 40.8 dB 0 0
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 5 5120 Ksym/sec 36500000 Hz 36.3 dBmV 2 Locked ATDMA 6 5120 Ksym/sec 30100000 Hz 35.8 dBmV 3 Locked ATDMA 7 5120 Ksym/sec 23700000 Hz 34.8 dBmV 4 Locked ATDMA 8 5120 Ksym/sec 17300000 Hz 34.0 dBmV
Current System Time: Sat Feb 13 09:39:43 2021
System Up Time: 0 days 1:50:30

Log from crash 5 days ago, 2/8/2021

Procedure Status Comment Acquire Downstream Channel 453000000 Hz Locked Connectivity State OK Operational Boot State OK Operational Configuration File OK Security Enable BPI+ IP Provisioning Mode Honor MDD IPv6 only
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked QAM256 8 453000000 Hz 5.6 dBmV 40.1 dB 0 0 2 Locked QAM256 9 459000000 Hz 5.3 dBmV 39.9 dB 0 0 3 Locked QAM256 10 465000000 Hz 4.9 dBmV 39.8 dB 0 0 4 Locked QAM256 11 471000000 Hz 5.9 dBmV 40.5 dB 0 0 5 Locked QAM256 12 477000000 Hz 7.0 dBmV 41.4 dB 0 0 6 Locked QAM256 13 483000000 Hz 7.2 dBmV 41.4 dB 0 0 7 Locked QAM256 14 489000000 Hz 7.3 dBmV 41.6 dB 0 0 8 Locked QAM256 15 495000000 Hz 7.4 dBmV 41.9 dB 0 0
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 5 5120 Ksym/sec 36500000 Hz 37.3 dBmV 2 Locked ATDMA 6 5120 Ksym/sec 30100000 Hz 36.5 dBmV 3 Locked ATDMA 7 5120 Ksym/sec 23700000 Hz 35.5 dBmV 4 Locked ATDMA 8 5120 Ksym/sec 17300000 Hz 34.8 dBmV
Current System Time: Mon Feb 08 14:21:24 2021
System Up Time: 0 days 0:27:52

[Natedeeeez]

I’ve been having the same issue. Random disconnects. I noticed that right before the issue occurs, there are a ton of “uncorrectables”. My ISP has confirmed the signal is very strong but something needs to be fixed in the modem/router. Netgear, is there a firmware update to fix this inconsistent and unstable connection???

[SJH13]

@Natedeeeez  No one has ever even looked at, much less replied to my inquiry.  There are, in fact, quite a lot of people, in the past who have had this exact problem.  Somehow they got responses, but not me, apparently

I gave up on ever getting any help from Netgear and my ISP, which is Xfinity.   

Instead, what I've done to solve the issue was to purchased a TP Link router.  Then I went into the settings on the Netgear Modem/Router and turned the Wifi function OFF and simply am using the Netgear product as a modem, and the TP link as the router. 

So far at least (it's been over a week) I have NOT lost wifi.  Before I did this, the Netgear Modem/Router was dropping the Wifi every few days, sometimes twice a day.  So, this might have solved the issue.   This is the second Netgear combination Modem/Router that has had frequent failures, the other one was a NETGEAR CM1150V  that I ended up returning to Netgear, because of the constant crashes.  Personally, I won't buy another combination modem/router, especially one from Netgear.  Good luck to you. 

My advice, try any other brand than Netgear.  They clearly have quality control issues now, and abysmal support, which is a shame, because for 25 years, I've only bought Netgear.  

[FURRYe38]

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. 
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...