I'm assuming this is a bug, because it wasn't in previous versions. Basically, when you click too quickly on different items in the left sidebar, MusicBee will refuse to change your selection. I exclusively use the Computer navigation tab to access my music, and very often I will click on folders and MusicBee refuses to select them. It works fine if you wait a second before selecting another folder, but if you click on two folders within approximately half a second of each other, the second folder will not be selected. This does not only apply to the Computer tab, but all items in the left sidebar. I'm guessing this behavior is due to the long double click to rename functionality (I don't know if you could double click rename in previous versions).
I love MusicBee by the way, it is by far my favorite music player. This is only a small annoyance that ruins the newest version for me.
To reproduce:
1. Click on multiple items in the left sidebar relatively quickly (within approximately 0.5 seconds or less).
2. Observe that only the first item remains selected, ignoring the other inputs entirely.