Get one of these so you can go fix it yourself tomorrow. 
It seems like the bridge mode implementation of Ovislink was the issue. I think it is possible to set the Eero 6 as AP and then connect it to the Ovislink as a router. I think that would fix your signal issue.
If possible, you can even disable the Wi-Fi on the Ovislink if you like.
I highly doubt that. I think the modem was dying as it was requesting public IP address like ten times a day. It was fine for over a year until mid June when it started giving me headaches.
If I remember correctly that’s how I had it set up originally. Good thing is that I had backed up the configuration file, so it will be easy to set it back again. Now that I remember, to set the Ovislink in a real bridge mode is like riding an elephant in a china store 
Funny that you mentioned that. There is a small airfield not five minutes away from the cottage. Long time ago I was thinking to get a pilot licence and buy a small aircraft, but I am afraid of heights 