I looked back into version control and set the property categories to what they were in a previous version. Works. I set it to a new category: Properties disappear from datatable editor. No caches, no old table assets, wth?
@Jambax Sorry to contact you directly, you helped me with a serialization topic a while ago:
Bug, UPROPERTY removed from the editor panel still overriding c++ values
Do you think this problem might be related to UPROPERTY serialization? I already cleared the caches and recreated assets based on the modified c++ struct but the problem remains. I suspect there must be some leftover data somewhere.