I am able to reproduce the issue by starting a (fake) call and covering/uncovering the proximity sensor for a bit (some times it can take some time but I always eventually get the problem).
It seems that powerd stops handling proximity events (although the kernel receives them) at some point. Pressing the power key somehow unblocks whatever is that has been blocked, and all queued events are then processed in quick succession. I don't know yet if it's a problem with powerd or some layer below it. Investigation continues.
I am able to reproduce the issue by starting a (fake) call and covering/uncovering the proximity sensor for a bit (some times it can take some time but I always eventually get the problem).
It seems that powerd stops handling proximity events (although the kernel receives them) at some point. Pressing the power key somehow unblocks whatever is that has been blocked, and all queued events are then processed in quick succession. I don't know yet if it's a problem with powerd or some layer below it. Investigation continues.