CM3000 – repeated T3 timeouts, SYNC failures, intermittent disconnects

I have a NETGEAR CM3000 (DOCSIS 3.1, firmware V6.01.04) in  VA on the 1.2 Gig plan. Download is fine (~1.5 Gbps) and upload is normal for my plan (~38 of 40 Mbps) when stable. The problem is repeated upstream instability:

• Event log: 27+ Critical T3 timeouts over ~33 days and escalating, including "16 consecutive T3 timeouts while trying to range on upstream channel 1 – retries exhausted," plus multiple SYNC timing failures
• Intermittent full disconnects; during these, upload collapses under 2 Mbps and latency spikes to 500ms+
• Upstream transmit power elevated at ~43 dBmV (on a ~10 ft drop, no splitters)
• Downstream clean (31 channels locked, good SNR/power, zero uncorrectables), but the OFDM channel shows very high correctable counts
• A technician already visited and confirmed the outside plant/drop are clean; issue persists
• Modem is on firmware V6.01.04 (successor to the pulled V6.01.03)

Please investigate upstream noise/ingress or a node-side issue, check my return-path SNR, and advise whether a firmware rollback to V5.0.x is possible. Reboots don't resolve it — please escalate beyond tier-1.