T3 ranging timeouts and SYNC failures - upstream pinned at 49-50 dBmV with Extended Transmit Power - requesting plant/maintenance check

Thanks Brian — did that just now, unplugged for 30 seconds at 12:03pm today. That was the first actual power cycle since this started. The reset showing in the logs on 8/29 at 2:26pm was a docsDevResetNow, which I believe came from the testing your team ran rather than a power pull, so this was a genuinely new step.

Unfortunately no improvement. Signal levels are unchanged before and after:

Upstream (ATDMA): 48.5 / 48.8 / 48.8 / 49.3 dBmV across channels at 16.4, 22.8, 29.2 and 35.6 MHz, with Extended Upstream Transmit Power enabled. Upstream OFDMA is 44.0 dBmV at 36.2 MHz.

Downstream: 2.3–3.3 dBmV, SNR 42.8–43.4 dB across all 32 channels — clean.

That combination is the reason I don't think this is the modem. Downstream is healthy, but the modem is running near the top of its transmit range with extended power turned on just to be heard by the CMTS. A power cycle can't change that, and it didn't.

Two things so today's data isn't misread on your end. First, the power cycle zeroed all the error counters — anything pulled now will show 0 uncorrectables. Before the reboot they were in the thousands. Second, there have been no ranging events for about 28 hours, but the longest quiet gap during the problem period was 27.4 hours against a 6-hour median, so that stretch isn't yet outside normal for this fault.

The history, from the modem's own event log: 34 critical events over 11 days (8/18–8/29) — 24 T3 unicast ranging timeouts, 6 SYNC timing synchronization failures, 2 T4 timeouts, 1 T2, 1 no-ranging-response T3. The T3s are spread across thirteen different hours of the day, which is what I'd expect from a marginal return path failing whenever conditions shift, rather than anything scheduled. There was also a cluster on 8/28 starting 00:27:37 — T4, T2, five consecutive SYNC failures and a T3 — with complete loss of downstream sync.

Modem is a customer-owned Netgear CM3000 (DOCSIS 3.1). CM-MAC [Edited: "Personal Information"], CMTS-MAC [Edited: "Personal Information"].

There's an existing ticket from chat on 8/29 — CR273986305. That was scoped to re-provisioning the modem's boot file. I asked twice during that chat for a line maintenance referral and I don't believe one was ever added.

Since a config re-provision can't affect ranging at the RF layer, could you get maintenance scheduled to check the return path — tap, drop and the feed to the house? Happy to provide the full event log and complete signal tables in whatever format is useful.