Failed reachability for IPv6

I configured the remote access for my nextbox a while ago and everything worked fine. A week ago I found that there was a warning in the “Remote Access” settings of the Nextbox app saying that the reachability test for the IPv6 failed (Resolving works). I am sure that this used to work before. The only change to the system I am aware of is an update for my Fritzbox (6591 Cable). Therefore I set up the DNS Rebind protection once again, rebootet the Fritzbox but didn’t get an improvement.
I have been watching this behaviour over some days and it’s strange that I sometimes can reach a Nextcloud Instance (hopefully mine) when directly putting the IPv6 into my browser but then its a http connection only and the Nextcloud does not let me login. On other days I can’t reach the IPv6 at all.
Since IPv4 is working completely fine I don’t have urgent problems. If anyone has an idea how to fix the IPv6 thing please let me know.

Generally this is hard to debug as the frontend lacks some more information and details of the reachability test, this will be updated with the next release (hopefully somewhere beginning next week)

Ok, so I’ll just wait for the update and report back what happens.
Thanks for the feedback!