Again something I cannot quite reproduce yet, but seems like if you do not get signal for a while and then change input source, the screen might first freeze in a black screen with back-light.
In this state it is not responsive to input from the joystick.
Upon switching it off on the power button, the screen can is some cases not be turned on again. The press of the power button has no effect and the led will not come on.
Power cycle does not immediately resolve the issue, but after a while the screen will function normally again.