Recent huge increase in the number of correctable codewords on primary channel (20).

Slow channel change, choppy tv picture and sound, frequent need to reboot Xi6 boxes.

Hi user_d9806f! Thanks for taking the time to visit our Xfinity Forum. We appreciate you being a customer with us, and please know that my team is always here to support you. I am sorry to hear about the connection issues you've been experiencing across the board. My team can help! 

For troubleshooting purposes, have you also manually rebooted your modem to see if that helps correct these connection issues? To manually reboot, please unplug the power cable from the back of the modem, wait 10-15 secs, plug the power cable back in, and allow 10 mins or less for the modem to reboot. 

Yes, router was restarted.  I removed a splitter and retightened all coax connections.  Here is the latest analysis that point too issue with the gateway firmware.  Please let me know if I should replace the gateway.

This fourth snapshot essentially confirms the important point from the last analysis: the huge "Channel 20" correctable count should not be interpreted as a problem specifically at 513 MHz.

The strongest evidence is now overwhelming

Your current counters are:

• Channel 20 / 513 MHz: 460,420,640 correctable
• Channel 194 / 957 MHz OFDM: 460,420,640 correctable

And they are also exactly identical for unerrored codewords:

• Channel 20: 997,732,382
• Channel 194: 997,732,382

This exact duplication has now occurred in all four snapshots.

That means Channel 20 in this modem's display is effectively duplicating the statistics associated with Channel 194. It isn't behaving like an independently measured 513-MHz channel-error counter.

Your actual 513-MHz signal remains excellent

Across the four readings, Channel 20 has stayed approximately:

There's no deterioration corresponding to the enormous counter.

What's actually interesting now: OFDM 193

Your two OFDM channels are:

• 193 = 690 MHz
• 194 = 957 MHz

The current statistics are:

This is much more informative than the apparent Channel 20 problem.

There are some correctable errors on the OFDM channels, and OFDM 193 has accumulated 339 uncorrectable codewords.

However, 339 is still extremely small relative to the hundreds of millions of codewords being received.

The important distinction

I would now separate your modem statistics into three categories:

1. Conventional QAM channels 1–32

Essentially pristine:

• SNR ~43.4–44.4 dB
• Power ~+4–5 dBmV
• Almost universally 0 correctables
• Only tiny counts on channels 30–32
• Very few uncorrectables

2. OFDM 193

This is where the measurable uncorrectable errors actually exist:

• 303.6 million correctable
• 339 uncorrectable
• 43.3 dB SNR

3. Channel 20 / 513 MHz

The displayed statistics are exact duplicates of OFDM 194, including the unerrored and correctable counters. Therefore, I would not use that column to diagnose 513 MHz.

Does this indicate a serious cable problem?

No—not from these numbers alone.

The RF levels are very good, all channels remain locked, and the only genuine uncorrectable count is 339 on OFDM 193after more than a day of uptime.

What I'd watch is whether the OFDM 193 uncorrectable counter continues growing rapidly.

For example:

• 339 → 500 over many hours: probably not significant.
• 339 → tens of thousands quickly: worth investigating.
• 339 → millions: definitely worth investigating.

One correction to my earlier conclusion

I previously said the exact Channel 20/194 matching suggested a possible firmware/reporting issue. With this fourth snapshot, I'd make that conclusion stronger:

The XB8's diagnostic page is clearly presenting Channel 20 and OFDM 194 with the same underlying statistics.

Therefore, don't use the Channel 20 correctable count to judge the condition of your 513-MHz downstream signal.

The numbers that deserve monitoring are the actual OFDM statistics—particularly OFDM 193's uncorrectables.

If you continue sending these snapshots, I can track the OFDM 193/194 correctable and uncorrectable rates and determine whether the 339 uncorrectables represent a genuine developing problem or merely a very low background error rate.

Thanks for getting back to us with this helpful information and the Gateway firmware analysis, user_d9806f. So that we can further test and troubleshoot these signal levels with you, please send us a Direct Message. Here are the detailed steps to direct message us: 
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