Audio-only call doesn't establish incoming audio connection for remote side

We have a setup with our own hosted HPB and janus+coturn as an MCU. When using the Talk iOS app and initiating an audio-only call, with the other side being in the browser (and therefore defaulting to a video call), quite often the receiving audio connection to listen to the other side fails to be established (the sending connection always works).

When initiating a video call instead from the app, everything works fine.

I already checked the logs of the iOS app, and there's nothing in there (I'd be happy to enable debug logging and share more logs if possible).

Looking at debug logs from Janus it looks like simply no candidate is chosen on the iOS Talk side.