I have corrupted two projects using paper2d sprites.
After corruption every time when I start my project some of the settings in my characters are set back to defaults (Use Controller Rotation Yaw, AI Controller Class, some custom variables).
Both times project was corrupted when I created custom material for sprites and started experimenting with lights.
Not sure if that helps but I’m using directional light in the scene.
My solution was to create new project and use planes instead of sprites.