Signal calls not connecting

I use nextdns android app on old samsung device(galaxy a9 pro) and it is causing issues in signal app. Whenever someone tries to call me, app gives a notification of connecting call, but it doesn't get connected. I turn off nextdns, and it connects the call.
I also use the private dns feature of my newer device(a galaxy s21), and there are no problems there.
I use only the official nextdns block list and steven black hosts file.
What to do?