Hey there, thanks for playing our game and this great review!
You are correct, there are some flicker problems with the introduction that started appearing after an update to the GB Studio engine, in the middle of our development, well after that code, and those sprites, had been created.
Happens in Potbound as well during the push/pull puzzle, but I didn't have time to address it in a Game Jam game.
I have, since then, figured out a hack around the flicker bug, which I have used successfully in Excelsior, but it requires extra resources. Unfortunately, the Mud Warriors introduction scene is already packed full with resources, up to the maximum limits. It would require a complete overhaul to get it working correctly again. Maybe someday :).
Good eye and, again, thanks for playing.