This is brilliant, love the style, love the dialogue, love the puzzles, great work!I also ran into the same error after completing level 3, but loading level 4 from the menu is a fine workaround.
Curse that edge case! I found a few others when fixing this one.
The issue comes up when the current level despawns right before an errant “level over” call is made
Glad you were able to play through the pain!