I recently migrated from iTunes to MusicBee, and it seems like line breaks aren't handled well in the lyrics. When I edit a song's tags (by pressing Shift-Enter) and go to the lyrics tab, most of the line breaks don't show up. So, it ends up being one (or a few) long lines of text, instead of being displayed on multiple lines, like it should be. When I had these same songs in iTunes, the lyrics showed up properly.
Similarly, when I show the Lyrics panel in MusicBee's main window, the lyrics don't show quite properly there either. In this case, a single line break is shown properly, but when there's 2 line breaks (as when separating a verse from a refrain), it only shows 1 line break. I can edit these lyrics to add any number of line breaks, then they show up properly both in the window for editing tags, and in the lyrics panel.
So, it seems to be an issue with how MusicBee processes existing lyrics, rather than an issue with adding line breaks. Maybe this is an issue with Windows vs Unix line break formats? It looks like the existing lyrics, that were added using iTunes, use a line break format that MusicBee doesn't support?