@jimp
I read on this very forum, and elsewhere as well that many users have the same problem, that is, it doesn't switch back to the main WAN when it gets back to work again and is available. Of course, it is not always the case, but unfortunately I was one of those who strumble upon it. As you said, there are always edge/corner cases that don't work as well as others.
For the time being, I run pfSense in a virtual environment , and as a test, I also installed and run OPNsense in the same scenario, then I set failover up on it and it worked smoothly. Anyway, I want to continue using pfsense since I like it most, but this issue can be a drawback.
Thanks