Sometimes An incoming call shows on screen and i can't do anything .. phone needs to be reboot that time
Happened to me once too. Can't answer or reject that call. Need to wait till the call hung up only can use again..
I have faced the same issue a few times
If it happens to someone frequently, then we can ask that person to log their phone with our log tool. Without this information, it will be very hard, if not impossible for us to find the bug.