I would suggest starting iTunes in safe mode to see if 3rd party plugins may be affecting it.
iTunes: Troubleshooting issues with third-party iTunes plug-ins
If the issue persists there, then I suggest testing to see if it happens in a new user.
Isolating an issue by using another user account
If it does work correctly in a different user then I suggest recreating the library altogether.
iTunes: How to re-create your iTunes library and playlists
All the best,