Hi, I apologize for the inconvenience this should not be happening, you will and should be able to get access to all the files after purchasing my bundle including the paid version inside the projects.
Have you tried accessing it from your "My library" under your profile and under "The things you own"? perhaps this issue is from Itch.io's side if still occurred and get in contact immediately.
By the way, thanks a lot for your support and feedback, please let me know your update.