I have had something like that happen to my game...
If you Save your game while many processes are running it will corrupt it.
I have had these things happen (I also removed all other than base script):
Not being able to press down
Not being able to move
A black screen
A error saying "Actor data not found"
A constant error saying "You have not set your default position"
A error saying "SyntaxError at Line 8: Graphics.freeze"