Systematic ~20-hour service interruptions with DOCSIS OFDM impairment — request modem firmware review and line inspection

I am reporting a chronic, highly regular service interruption pattern affecting my Comcast (AS7922) connection, documented over a 14-day monitoring window (September 16–30, 2026).

Equipment: Customer-owned ARRIS SURFboard S33 (retail-labeled S33v2), hardware version V1.0, firmware TB01.03.001.11_051722_212.S3 (dated May 17, 2022). DOCSIS 3.1, provisioned on the 312/20 Mbps tier.

Primary finding — periodic whole-connection outages every ~20.2 hours. Over 14 days, my independent monitoring recorded 15 whole-WAN outages (34 minutes cumulative downtime, 99.83% uptime). The interval between consecutive outages was 20.0–20.5 hours across thirteen consecutive occurrences — a periodicity too regular to be incidental line noise. Each event: (a) takes the connection fully dark, including the first Comcast hop (po-108-rur202.bluelight.tn.knox), (b) lasts 2–3 minutes, and (c) recovers with hops returning in sequence within roughly 30–90 seconds, consistent with a cable modem re-ranging and re-registering. My modem's event log and uptime confirm it re-initialized immediately before at least one of these events (September 29, 18:39). Because only the cable operator can update retail modem firmware, I request that you review the firmware currently provisioned for the S33 v2 and push any available update; the installed build is over four years old and has been associated in public reports with recurrent connection drops on this exact model and revision.

Secondary findings — sustained DOCSIS impairments:

1. OFDM channel 193 uncorrectable codewords: approximately 111,000 per day sustained across the entire window, despite signal levels within specification (downstream SNR 40.7 dB, downstream power 3.8 dBmV, upstream power 44.3 dBmV). Modem CM-STATUS event log entries on channel 193 (types 16 and 24, OFDM profile transitions) coincide with outage recovery.
2. Upstream ranging instability: eight T3 timeout events between 02:43 and 05:17 on September 30, coinciding with a monitored latency/jitter excursion on the local Comcast segment (po-108-rur201, jitter to 18 ms). This suggests upstream path or plant impairment rather than in-home wiring.
3. Elevated baseline latency: 15.9 ms first-hop idle latency, above the normal range for DOCSIS, further suggesting upstream-path impairment.