Got some news today that might be interesting.
I posted another issue yesterday about my camera not working anymore (here : Camera not working anymore on FP3 since migration to v1.0 - #5 by SebastienL) and I just realized that my camera is not working AFTER a failed attempt to make a call with Signal / WhatsApp.
It’s like this failed attempt to make a call is making the camera module unavailable, so I guess we can also imagine the camera module might be the source of the bug with the call.