Modem logging constant T3 timeouts

Sporadic drops, buffering, and general slowness for over a week.

Had a tech out — he said my UniFi UCI modem was the issue. So I swapped it for an Arris G36 in bridge mode. Different modem, different vendor, exact same problem. Confirmed on my own network monitoring.

Pulled the Arris event log. Tonight 8:39–8:41 PM: 21 T3 timeouts and 11 loss-of-sync errors in two minutes, plus lock failures on downstream channels 4, 5, 6 and OFDM channel 193.

Checked signal levels 48 minutes later and everything was clean — downstream +1 to +5 dBmV, SNR 37–39, upstream high 30s, all locked. So it's intermittent, which is likely why the tech found nothing while he was here.

Questions:

• Who do I talk to about T3 timeouts and line errors?
• Who can check my modem against the CMTS flap list?
• Who can look at upstream ingress on my node?