Sorry I couldn't help you out with some support. I don't go here often anymore. But I see Violet has been his usual helpful self.

I would recommend that if you want to prevent having these issues again, it would be better to refrain from renaming any files in the future. I haven't tested many non-standard J1E cases so it's probably wisest to stick to the sprite and blocks files that have the same extension as the level.

I'm still piecing together a new version of J1E that should do a better job (and also incorporating multiple tile select, and much better memory use) but it's still going to be a while.