In Video Room, one participant can't be heard by the others

### Steps to reproduce

I was told to open this ticket on an issue I reported to the #webrtc matrix room.

We've got a video room, created at about the time when the Jitsi → Element Call migration happened. We used the room for months without serious problems. Until recently:

In that room, there were 3 participants in an actual call on 2025-04-07 from 18:20 to 18:22 UTC:

- A, on Element X (Android) 25.03.4
- B, on Element Desktop (Linux) 1.11.96 – affected?
- C, on Element Desktop (Windows) 1.11.96

**Participant B could not be heard by the others.** Participants A and C could be heard by all others, including B.

And here is the kicker: I invited the same participants into a fresh (non-video) private room and started a call there, and it worked without hitches for 4 hours until we called it a day.

This issue is reproducible, we had it on multiple days and on different LiveKit SFUs (including matrix.org's). It happens with 2 or 3 participants. However, it only started a couple days ago. We *were* using that video room for months without serious issues, and also with the (now) affected participant. The issue started at around the time when Element Call was embedded into Element.

I told everyone to check for latest versions of clients. And at least from participant C I got confirmation he was running 1.11.96 (latest).

We never checked video, we're only using audio. The avatar image that is replacing the video was in general only showing a capital letter, despite us all having set up an image. I was told on #webrtc that this is a known limitation. **However, the avatar image of affected participant B was behaving strange, it was only shown as a "B&W YouTube" icon (see screenshot below) for quite a while before it finally was shown as a capital letter.

I will try to provide as many logs as I can.

### Outcome

see above

### Operating system

_No response_

### Browser information

_No response_

### URL for webapp

_No response_

### Will you send logs?

Yes