Silent Knight System Error

Got a co-worker who is running into two panels now that are getting an occasional "System Error", need to power cycle the panel, let it sit off AC power for 15 minutes, then power up to clear it.

The customer thinks we are making up the answer that a new panel is required. I ran into this issue back in 2018/2019 and never got an answer as to what the problem is. Any ideas? And yes, I know the best solution is put in something else but...