On my Win10 machine rating a song via the taskbar-miniplayer is sometimes not possible.
Although clicking 3 or 4 times on the +* button only the first click works correctly which results in half star rating for the song.
This is not always the case so it is difficult to reproduce this bug intentional.
On my machine I guess it happens about 5 times when rating 20 songs.
This is an old bug which happend ever since as far as I remember.
MusicBee 3.2.6793
Win 10 Pro - Version 10.0.17134 Build 17134