Microphone emit no sound to the others

Steps to reproduce

Receive a talk call
Answer the call, voice only
You hear the other participant, but it does not hear you
Toggling microphone mute/unmute does not change the problem

Expected behaviour

Both sides should hear each other

Actual behaviour

I was hearing perfectly the other, he was not.

On my side, an android phone, on the other side a iphone.
Having a call with the same participant on his phone, using the web version of talk, it works perfectly.
So, problem is from the android phone.

Authorizations have been checked, use of microphone is OK.

No error message.

Device brand and model

HUAWEI EML-L09 (P20)

Android version

28

Nextcloud Talk app version

18.1.0

Nextcloud server version

28.0.4

Talk version

18.0.6

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

Nothing on the server log that day

Additional information

No response

Start by reproducing the voice-only call on the reported Huawei P20 running Android 28, with the custom signaling, TURN, and STUN servers configured. Trace the Android Talk audio-call path and compare it with a working web call; done means both participants can hear each other and microphone mute/unmute behaves correctly.