Today happened two times: FP2 runs out of battery and turns off. I plug-in the power adapter (usually working fine), phone goes into charging mode, I press power button and phone goes on until home screen.
Trying to swipe the screen for unlocking it does not react (actually this morning camera icon was like moving).
Holding 15+ seconds power button does not help.
Only way out is remove the battery, then after place it back everything is back working fine.
Is your screen unresponsive while it’s plugged in? Because that is a well know problem. In this topic (Fairphone 2 unusable while charging) there is an explanation.