This issue has persisted across sessions and system reboots. If I load an earlier autosave I am able to change categories. My completely uneducated guess is this has something to do me having hundreds of unused cards in inventory, but idk.
I was planning on posting a save file, but there seems to be a (reasonable!) restriction on new accounts posting links or files, so looks like I can't do that

e: a friend tried the save and confirmed that they see the same issue.