I have just discovered that since the scrolling was changed from horizontal to vertical, selecting a letter on the direct jump bar will not work properly if there is a title containing non-alphanumeric characters in it.
For example, I have Æon Flux in my movie library. If I select any letter to jump to other than # or A, it only scrolls as far as that movie. This didn't happen in the previous version when the scrolling was horizontal.
The folder and file name for this movie is Aeon Flux (2005), but the metadata was automatically set to Æon Flux (the title according to TheMovieDB and IMDB). I fixed this issue for myself by manually renaming Æon to Aeon in the metadata manager.
Renaming titles obviously won't be the ideal solution long term...