Sprites Turning to Cubes Instead of Original Sprites

I’m working on a game, and the character sprites suddenly were replaced with red/green squares. How do I fix this? @grazer

I had this problem before, my chromebook crashed, leading to it restarting, most of the sprites returned, but others stayed that way and I fixed them. It’s probably not the best solution though. Also if you have bugs like these, report them to grazer by typing: @grazer