Recurring internet drops with a customer-owned Arris S33 modem and need help investigating a DOCSIS connection issue.

I'm having recurring internet drops with a customer-owned Arris S33 modem and need help investigating a DOCSIS connection issue.

The same S33 has experienced these drops at two different Xfinity locations in two different states (Cambridge, MA and Knoxville, TN). I originally had an eero modem/router that experienced the same issue; I then replaced it with the S33 + TP-Link Deco mesh, and the drops continued.

The S33 is connected directly to the coax wall jack with no splitter.

The modem's downstream signal looks excellent (0–2 dBmV, 42–44 dB SNR, 0 uncorrectables), but the event log shows:

• "UCD invalid or channel unusable"

• "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing"

• Upstream diplexer changes between 5–42 MHz and 5–85 MHz

The upstream transmit power is approximately 46–47 dBmV.

The S33 is running firmware TB01.03.001.10_012022_212.S3, hardware V1.0.

I'd like to have an Xfinity technician check the CMTS-side diagnostics for this modem, particularly upstream ranging/T3/T4 errors, return-path noise, provisioning, and whether this is the current approved firmware for the S33.

Can Xfinity Support please review this and let me know if I should send a DM with my account information?