Today i woke up with router reset to factory settings, after a power outage (but I have a UPS upstream of router i don't think it actually lost power, that was the only "extraordinary" event, not sure if impacted or not, just putting on the table)
Just want to add another data point for these initial spontaneous factory resets being somehow power-related: After
dealing with a spontaneous reset last year (which I concluded was not a result of a storm, but now I'm questioning that), I put the router in question on an old APC UPS (model APC BackUPS 280 if I remember correctly) with a brand-new battery. About a week ago, a spontaneous reset happened again, and wouldn't you know it, on the same night as a bad storm. (Fortunately, unlike others here, restoring the configuration from a saved backup survives reboot.)
Assuming it's not an extraordinary coincidence, this suggests two possibilities to me for what's causing the spontaneous resets:
1. (Standard thinking) It's power supply related and the UPS still suffers a brief drop of output current or power spike due to a brownout, and the R7800 is highly sensitive to this (though it doesn't explain why power loss from pulling the plug to reboot it doesn't cause a factory reset).
2. (Speculative) A post-brownout power spike is hitting the client devices attached via Ethernet, and one of them is sending current over the Ethernet cable, overloading the R7800 and causing the factory reset.
I'll note that none of the connected Ethernet devices are powerline adapters, and I believe all directly-connected devices are on relatively new surge protected power strips.
I'm curious to hear opinions on this, especially the second, more speculative possibility. If it has merit, maybe I could prevent this happening again by only plugging one gigabit Ethernet switch into the R7800 and all devices into that, in attempt to shield it from any power spikes over Ethernet cabling.
I'll be looking to replace this router soon regardless.