Wondering if logic can be applied to combine items that should be combined?
For example: Sci-Fi, Science Fiction and Science-Fiction are all listed in my relatively clean Genre list.
I used to have this as well in my library. Discovered it was caused by metadata files stored in the same folder as the movie. Once I removed these files and did a full reload of all metadata, it correctly retrieved genre information from themoviedb.org.
You can test this by removing one of the metadata files on a movie that is not coded the way you expect and force a reload of metadata via the “Edit” function