CM1150v extremely unstable critical(3) - Started Unicast Maintenance Ranging and SYNC timing errors

[saigkrish]

Team,

 I have  a xfinity 600Mbps plan. The Cable modem I have is CM1150v. I have hooked one Netgear wifi-router via ethernet connection from the CM1150v<-->NetgearR6700. Over the last 2 weeks, our internet is very unstable. When it works, it gives 600Mbps but then the connection abruptly stops and I have to reboot the cable modem. I already had a tech visit from xfinity on 11/26. He did the cable testing, he did the ethernet from the CM and he did a test on the wifi-router. All were good during his visit. But over the last 3 days, it went from bad to worse. 

I ran an ethernet cable directly from the CM1150v to my laptop to rule out any issues on my wifi-router. The problem still persists. All the lights on the CM1150v are stable. But when I looked at the event logs, I see a repetitive high frequency Critical(3) errors.

In case the picture doesnt appear, pasting the text .. these errors go in a cycle.

TimePriorityDescription

Fri Dec 04 00:39:19 2020Critical (3)Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:80:88:d4:cf:40;CMTS-MAC=00:01:5c:62:fc:5e;CM-QOS=1.1;CM-VER=3.1;

Fri Dec 04 00:18:55 2020Notice (6)CM-STATUS message sent. Event Type Code: 5; Chan ID: 48; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=28:80:88:d4:cf:40;CMTS-MAC=00:01:5c:62:fc:5e;CM-QOS=1.1;CM-VER=3.1;

Fri Dec 04 00:18:50 2020Critical (3)Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=28:80:88:d4:cf:40;CMTS-MAC=00:01:5c:62:fc:5e;CM-QOS=1.1;CM-VER=3.1;

Fri Dec 04 00:18:38 2020Notice (6)DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=28:80:88:d4:cf:40;CMTS-MAC=00:01:5c:62:fc:5e;CM-QOS=1.1;CM-VER=3.1;

Fri Dec 04 00:18:33 2020Notice (6)TLV-11 - unrecognized OID;CM-MAC=28:80:88:d4:cf:40;CMTS-MAC=00:01:5c:62:fc:5e;CM-QOS=1.1;CM-VER=3.1;Time Not EstablishedNotice (6)Honoring MDD; IP provisioning mode = IPv6

Time Not EstablishedCritical (3)SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=28:80:88:d4:cf:40;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;

Appreciate any help on resolving this

sai

[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. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...

[decosse]

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@saigkrish wrote:

Team,

 I have  a xfinity 600Mbps plan. The Cable modem I have is CM1150v. ... Over the last 2 weeks, our internet is very unstable. When it works, it gives 600Mbps but then the connection abruptly stops and I have to reboot the cable modem.

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 @saigkrish I had exactly same issues in about the same timeframe - my internet speed is/was, as yours, excellent when it works then dropped off during course of day until non-existent or only few Mbps; power cycle of Modem brought it right back - EVERY morning I would have to reboot the CM1150V as I had no signal at all  - this just started suddenly, interestingly about the same period as yours (I'm in Bay Area CA, where is your service?). 

Similarly Xfinity tech came out after about 2 weeks of this and checked all my wiring for losses all way back to the street interface (all perfect) 

He installed an Xfinity Modem and it was back to full speed (for 2+ weeks now has been perfect) 

I had to argue the point with multiple Netgear Agents till I finally got acceptance for an RMA - my (valid, I would add) argument when they initially insisted on being able to access the modem on-line, is that they seemed to fail to grasp that to re-install, it requires having Xfinity to re-provision the modem (and then of course again, to go back to the Xfinity Modem) - I maintained that it was really simple: major problems with the Netgear, none with the Xfinity; fundamentally that concludes the problem is with the CM1150V. 

I am currently waiting for the replacement - the RMA system would not accept a credit card (any!) through about a week of trying and I had to settle for the 'ship first, wait for receipt by Netgear, then Replacement ships" plan

When my replacment arrives of course I will have Xfinity re-provision it and report back on results (I don't expect that for about another week)