Why doesnt my screen come back on after pushing lock button?

When ever I press the lock button to turn off the screen or the screen times out and turns off it will not come back on. if I push lock button and swipe as if Im unlocking the phone you can hear it unlock. then by tapping around on the screen the haptic feedback is working. the phone is not off or frozen. the screen doesn't come back on until I hold the power button until it reboots. screen works again until once again locked. this seems to be an intermittent problem after playing around with settings. last settings I change were keyboard functions. first time this happened I changed a display setting called miravision. when I reverted the change the phone worked normal. but this time I changed a keyboard setting.