just call the registration, choose another style, choose the prior ( in the registration ) used style again and save the registry again ( overwrite ). So you donīt have any issues regarding styles, bass, chords and so on
Greetings from East-Frisia ( Northern-Germany )
Loc: South Africa
Hard to say as some older registrations work & some not. I really want to emphasize that not reading older registrations correctly seems to be the ONLY problem with the new OS. There is not a general problem with registrations, just with pre OS5.3 registrations. So it should work just fine for almost all users. Don't shy away from the update unless you created many fancy registrations before.
Make sure you'll fly forever!