Android app call accept fails on Volla YOS 15 with microG (browser works)

Steps to reproduce

Steps to reproduce:

Install Nextcloud Talk Android app via Aurora Store on a Volla phone running YOS 15 (or any AOSP) with microG enabled.
Configure and log into a working Nextcloud Talk server.
Notifications and chat messages work correctly.
Start or receive a voice/video call from another user.
Answer the incoming call on the Volla device.

Expected behaviour

The call should connect normally and both users should enter the call session.

Actual behaviour

As soon as the call is accepted, the other participant immediately sees that the Volla user has left or hung up the call.
On the Volla device the phone continues ringing or remains stuck trying to connect.

Device brand and model

OwnPhone

Android version

15

Nextcloud Talk app version

23.0.1

Nextcloud server version

Nextcloud Hub 25 Autumn (32.0.8)

Talk version

22.0.12

Custom Signaling server configured

Yes (specify version in Additional Information)

Custom TURN server configured

Yes

Custom STUN server configured

Yes

Android logs

No response

Server log

Additional information

Chat and push notifications work correctly.
Calling itself works until the accept phase.
Browser-based Talk calls on the same device work correctly.
Battery optimization is disabled for the Talk app.
Device: Volla Phone / YOS 15
microG enabled
Installed through Aurora Store

This looks similar to Android signaling/WebRTC issues already reported in:
#5802

Start at the Android call accept phase and reproduce the failure on a Volla Phone running YOS 15 with microG, comparing it with browser-based Talk calls. Review the related issue #5802 and collect Android and server logs; done means an accepted call connects both participants without continued ringing or an immediate hangup.