Could it be that the domain name has both IPv4 and IPv6 and depending on the network you try to reach one or another? Wireguard can work on both protocols, but from my experience it doesn’t try both to see which one works (like browsers do). So if at the first try the dns resolves the “wrong” IP version, wireguard cannot connect and doesn’t fallback trying the alternative.

Not anymore, it supports txt records now

For a simple dynamic DNS, I have been using https://www.duckdns.org/ for a few years and been happy so far

The main storage is a Nas that is mounted in read only most of the time and has two drives in raid mirror. Plus rclone to push a remote and client side encrypted backup to backblaze.