Recurring T3 Timeouts, DOCSIS Loss of Sync, Abnormal Codeword Counters, and OFDMA Power – Arris G34

I'm requesting assistance from Xfinity's technical support team with investigating intermittent connectivity problems affecting my customer-owned Arris SURFboard G34 DOCSIS 3.1 gateway.

I've experienced recurring connection instability, DOCSIS synchronization errors, and some very unusual modem statistics over the past several months.

1. Current upstream signal readings (October 31, 2026)

My G34 currently reports:

• Upstream OFDMA power: 53.9 dBmV

• OFDMA frequency range: 39.9–84.3 MHz

• OFDMA modulation: 2048-QAM

• OFDMA status: OPERATE

• Upstream SC-QAM power: approximately 44.5–45.3 dBmV across four channels

• Downstream QAM power: approximately +5.2 to +5.9 dBmV

• Downstream SNR: approximately 40.4–40.9 dB

I understand that OFDMA transmit-power reporting may differ from conventional SC-QAM measurements, so I'm not assuming the 53.9 dBmV reading automatically establishes an out-of-spec condition.

However, combined with recurring T3 ranging timeouts and intermittent connectivity problems, I believe the upstream RF conditions warrant investigation.

2. Extremely unusual CM Error Codeword statistics

My G34 has also repeatedly displayed what appear to be abnormal codeword counters.

On August 30, 2026, the modem showed an alternating pattern of:

• Approximately 3.09 billion correctable codewords on certain channels

• Only a handful of unerrored codewords, sometimes zero

• Zero reported uncorrectable codewords

• Other channels displaying zero or seemingly frozen counters

On October 31, 2026, a similar pattern appeared again:

• Approximately 1.2 billion correctable codewords on alternating rows

• Only 0–4 unerrored codewords

• Zero uncorrectable codewords

These readings seem internally inconsistent and may represent a G34 firmware issue, incorrect counter mapping, or inaccurate statistics rather than actual RF errors.

I would appreciate clarification on whether this is a known reporting problem with the Arris G34 or whether there is an underlying DOCSIS issue.

3. Previously documented DOCSIS synchronization errors

My August 30, 2026 event log included:

• 03:52:22 – Critical: "SYNC Timing Synchronization failure - Loss of Sync"

• 03:52:24 – "CM-STATUS message sent. Event Type Code: 5; Chan ID: 28"

The CM-STATUS event followed the synchronization failure by approximately two seconds.

I've also observed recurring T3 ranging timeouts.

I would like to determine whether these events indicate intermittent upstream impairments, loss of DOCSIS synchronization, or a separate modem-related problem.

4. Previous gateway instability

During an earlier incident in late August, the gateway experienced broader connectivity problems affecting its network functionality. Normal operation returned after a power cycle.

That raises the possibility of a gateway firmware or hardware issue in addition to a potential cable signal problem.

I'm not ruling either possibility out.

5. Unsuccessful Xfinity support interaction (October 31, 2026)

I contacted Xfinity support and specifically requested that an agent inspect the live upstream RF signal measurements and historical ranging errors from Xfinity's side.

Unfortunately:

• The automated troubleshooting system declared my connection healthy and concluded the problem was unrelated to Xfinity.

• The live agent did not provide upstream RF measurements or ranging diagnostics.

• Instead, I was told the modem was receiving approximately 934 Mbps download and 400 Mbps upload.

• The representative proposed sending refresh signals and modifying the modem's boot file without first verifying the suspected RF issue.

I declined those changes because I wanted the underlying problem investigated before modifying a functioning modem configuration.

6. What I'm requesting

Could an Xfinity technical support representative assist with the following?

1. Check the CMTS-side upstream receive levels, MER/SNR, and ranging history associated with my modem.

2. Review OFDMA channel performance, upstream power behavior, and any relevant profile or ranging adjustments.

3. Determine whether the recurring T3 timeouts and previous Loss of Sync event correlate with signal impairments or other network events.

4. Check whether other modems sharing the same upstream service group have experienced similar issues.

5. Clarify whether the abnormal CM Error Codeword statistics are a known Arris G34 firmware/reporting issue.

6. Determine whether a field technician should inspect the coax connections, service drop, and street tap.

I'm not claiming that every abnormal statistic necessarily indicates a physical line fault. I am trying to distinguish among an upstream RF problem, inaccurate firmware reporting, and a possible gateway malfunction.

I have screenshots of my modem statistics, historical error logs, and the full October 31 support transcript available.

I would appreciate an actual technical investigation rather than another automated speed test or routine modem reset.

Thank you.