CM1000 Xfinity activation woes - reprise

My xfinity leased arris box died a week ago so I bought a CM1000 from Amazon and self registered it. It worked fine for 48 hours, then my internet was blocked and each time I tried to access a web site I was presented with the xfinity registration page.

I logged in with my xfinity account, the credentials were accepted, the address at which service would be activated was correct, but when I pressed the button to activate service I receive the error message

"Sorry we couldn't find this device"

Several calls to xfinity later, several modem resets, no change and a tech was called out.

While waiting for the tech, I discovered that a VPN access point at home, which connects back to my work place, was able to establish a connection and I could access internet through the VPN which was passing through the CM1000 cable modem

The tech arrived, confirmed that the coax signal was fine, he sent an activation code to the modem, it re-started and full service was restored.

18 hours later, the problem returned. Calls placed to xfinity, an hour wasted with the Calcutta call center, a tech was scheduled.

The tech arrived later that morning, the coax looked good. The tech spent 2 hours waiting for tier 2 support to answer his call on hold.

Eventually tier2 support asked us to unplug the router, the tier2 tech sent an activation code, the modem restarted, I turned on the router and all was fine - for 18 hours.

This morning, the same error message when I log into to xfinity's self activation page.

The CM1000

Hardware Version 2.02
Firmware Version V3.01.06
Cable Modem Serial Number 4L058CW9007B3
CM certificate Installed
CM MAC 3c:37:86:e9:27:80

I looked at the logs in the CM1000 too,

Time Priority Description
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=3c:37:86:e9:27:80;CMTS-MAC=00:01:5c:6b:a8:66;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Warning (5) ToD request sent- No Response received;CM-MAC=3c:37:86:e9:27:80;CMTS-MAC=00:01:5c:6b:a8:66;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) TFTP Request Retries exceeded, CM unable to register
Time Not Established Critical (3) TFTP failed - Request sent - No Response;CM-MAC=3c:37:86:e9:27:80;CMTS-MAC=00:01:5c:6b:a8:66;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Warning (5) ToD request sent- No Response received;CM-MAC=3c:37:86:e9:27:80;CMTS-MAC=00:01:5c:6b:a8:66;CM-QOS=1.1;CM-VER=3.1;
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=3c:37:86:e9:27:80;CMTS-MAC=00:01:5c:6b:a8:66;CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=3c:37:86:e9:27:80;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2019-05-25, 10:14:19 Critical (3) Resetting the cable modem due to docsDevResetNow

Tomorrow a tech will arrive, the 3rd in 4 days. I'm sure they too will be stumped. But at some point, the router will be turned off, tier2 support will send an activation code from the CMTS and I will probably have service restored  - for 18 hours.

For added information, my zip code is 94608, the North Oakland area. I have no idea which brand of CMTS is being used, but since the cable modem firmware version appears to be up to date, and my xfinity account recognizes this modem is associated to the account. I can only assume there is a communication problem between the CMTS and the modem.

Has anyone else seen this scenario ?