When it happens on mine, my doorbell literally will go offline, and as you mentioned seems like it has to restart and is completely unavailable for a few minutes until it comes back. In that case Rapid Ring will not work either.
I agree on a software issue. Had no issues for about 2 years, now it’s junk. My doorbell is stuck on firmware version 2.1.01005 (does not say “Up-to-date”). Not sure what the current firmware version is, as I don’t see Ring publishing that anywhere. It has a strong wifi connection and voltage says “Good”/4022mV.
I haven’t had much time to mess with mine but hopefully will soon. If you get yours figured out please let me know, I’ll do the same. If someone at Ring could actually be helpful… please also feel free to chime in.