I've tried updating, reverting, all to no avail.
Hmm. That's unfortunate. Older Unreal builds can be tricky some times. The Steam version is slightly newer - it might be worth trying that one.
If you bought Bonbon on here you should be able to access a steam key.
If you got Bonbon for free or in a bundle, itch won't give you a key, but since you're having issues, if you email me at aethericgames at gmail dot com, then I'll reply with a steam key.