Private DNS on android not working with IP6 only address

[Cilenco]

I have used Adguard Home for a long time on a VServer with an IP4 and IP6 address on the internet using DOT. Lately I have changed it to a Raspberry in my home network with only has an IP6 address. I have pointed the AAAA record of my domain to my raspberry and I'm able to access the Web interface from my smartphone even when I'm on mobile data.

When I set the private DNS (DOT) on my Android (14) phone however I get the message, that the DNS server is not accessible from mobile data. Within my and others WIFI it works great but it will not work with mobile data. I'm not sure if this is a problem with Android or my home setup. I have an IP4 and IP6 address in mobile data and I'm able to access the Web UI.

Do you have any ideas how I can debug this or is this a known problem? Im currently on 107.48