How to fix: screen doesn't turn on after call

Screen turns off during a call (expected) but there is no way to turn it on, even after the call ends. I have to turn off the phone by holding the power button for 10 seconds. I have tried tilting, shaking the phone, touching the screen, pressing the power/volume buttons. The only thing that works is to use a bluetooth headset so that the screen doesn't turn off in the first place.