C7000 AC1900 losing all settings when unplugged

Several times over the past year, I've lost all settings when the power was briefly disconnected -- and I lost them once when, as far as I know, nothing happened.The first time was very soon after initial install, so I called Netgear tech support (thinking there was something wrong with the router) and they insisted that the only way it could have happened was for someone to hack into my system and do a reset, or for the reset butting to be pushed. Um... no, that didn't happen. To confuse things even further, there have been other times that I've brielfy unplugged and the settings were not lost.

This puts my admin password back to the default and the SSIDs back to default names and passwords. So I no longer have wireless access to check or fix anything until I can go in and change the settings back again. Yes, I have the settings backed up and can restore from a file but I shouldn't have to do this!

Firmware is up to date.

"Don't power down" is an obvious answer but it's not even remotely an acceptable answer.

Not sure if it's related or if it's a separate issue but I'm noticing that the event log is showing "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing" with a time of 1970-1-1. I have no clue how often this is happening because they're all at around time 00:00:30. The last event log that's not that time was timestamped at just about the time I unplugged the unit.  The regular log shows a similar set of issues with everything before that time stamped at 1970.

Any ideas on what might be happening here?