Weird - bridge has worked flawlessly for me for the last couple of years. I use Thunderbird with it. They had clear instructions on how to configure it in just a couple of clicks and I haven't had to mess with it since then.
My ONLY complaint is that if I launch Thunderbird before Bridge has finished, it won't connect. That can be fixed by waiting first, or opening the app on a schedule, or just closing and re-opening it. (I choose to use a scheduled app open)
I don't think that's a normal experience. It may be worth contacting Proton about it and asking for support, assuming you still pay for service. May be an easy fix. Or it could be on TB's end.
I'd also check if you have any unusual network configuration (PiHole, router settings, etc) and see if those could be interfering somehow.
Though since it's intermittent it may be hard for them to track down.
My ONLY complaint is that if I launch Thunderbird before Bridge has finished, it won't connect. That can be fixed by waiting first, or opening the app on a schedule, or just closing and re-opening it. (I choose to use a scheduled app open)