I purchased the Mini Fantasy Complete Bundle in March. Meanwhile, new items were added to the Mini Fantasy Complete Bundle, but my list wasn't updated. I am reluctant to purchase a new bundle as most of the items are duplicates. Why isn't it updating?

Generally item granted in a bundle are fixed at purchase time (to prevent items being removed). If the developer wishes to grant new items to existing buyers then they need to reach out to itch.io staff to facilitate that.

Hope that helps