While waiting for 1.2, I decided to try to do a find/replace of any references to title.p8 in the level files to another filename. I tried astra_and_the_new_constellation.p8 and then renamed title.p8 to that. But just making that small change broke the transition from the cart_formerly_named_title.p8 to the level files. It just stops at the end of the loading animation. No idea why. I'll keep trying, but if you have any other suggestions or thoughts as to why it might misbehave, let me know?
EDIT: I tried astra.p8 instead of the full title with underscores, and that didn't help either.
EDIT 2: While trying to figure out the problem, I also realized if the files are not stored in the root of /carts, they don't transition either. But even when I store them all in carts instead of a subdirectory (which would be my preference, as I have other multi-file itch carts I'm trying to keep organized), I still can't manage to rename in the code them without breaking the transitions. I'm officially out of ideas now.