It used to be there because I had to change a few. Strange….
Sorry about that.
Normally I would suggest going through and removing the category selections from your posts, deleteing the old categories, creating new ones from scratch, and then reassigning them but that would be a royal pain. I *think* that here it’s tied to the category ID number instead of the category name.
Go ahead and submit a feedback or contact them directly and ask them if they can look into this.