Same issue. Should it say (DEBUG) in the title?
I also noticed the hierarchy in the spritesheets folders seems different from the .exe. If I go into heads in the spritesheets folder I see arms, backpack, etc.. but the first level in heads in the exe. is Alien, Boarman, etc.. I don't know how the program runs so it may be intended to work this way but I thought I would call it out.