Extremely High Latency, Intermittent Issues Causing 3000ms+ ping

Recently, the internet has been going completely crazy (3000ms+ intermittent ping 3-4 times per week or more for hours sometimes), Xfinity technicians have been out multiple times, but has not been able to solve the issue.

Network specifics:

Arris SB8200 and Orbi Wifi 6 Mesh network with router and 2 satellites

I have about 50 devices on my network at any time (some IOT, some Apple TVs, and other standard devices)

I have clear signal, not too many neighbors, so Wifi SNR is very good.

Symptoms:

Network completely comes to a halt with 3000+ms ping times multiple times per week.

Sometimes if I remove a device or two from the network, it appears to improve, but regresses again shortly.

Some days, it will be perfect with no issues. Other days, it will be terrible most of the day (like today).

Attempts to resolve:
1. Hard reset router

2. Hard reset modem

3. Configured with new SSID to isolate the issue being from a device and slowly added devices over time.

4. Remove devices one by one from the network (sometimes this helps fix the issue, but it seems like it doesn't matter which device I remove...i.e. there's no rogue device).

I've spent dozens of hours trying to track this issue down and have come to a dead end. After another hard reset of the modem today, these are the numbers & errors I'm seeing if this helps:

Common errors in the logs from the Arris SB8200:

"UCD invalid or channel unusable;"

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

Connection Status from Arris: