FurryNutz: Sent you a PM, going to review settings at some point. I'd appreciate it!
In the meantime, I haven't re-created my settings from scratch after I did a factory reset. I simply imported the settings from the file. Does recreating the settings from scratch really make a difference? Seems to me this if the backup settings file is corrupt, the restore process would break at some point. Recreating from scratch would be a major pain, as I have network filtering enabled, DHCP reservations on ~20 devices. Plus the other global settings.
I keep going back to a firmware bug with this issue... even if there's a Wifi interference issue in my case, it shouldn't cause the router to reboot itself. Perhaps the Wifi client device causing the issue is disconnected and subsequently reconnects to the router. But a total system shutdown seems to be firmware issue, i.e. the DIR 655 isn't failing gracefully, in software engineering lingo. Could also be a hardware issue with my router. Are there any diagnostic tools that I can run on my DIR 655 to verify that it's functioning properly?