changing an instrument in Mixer while project is playing leads to unexpected/incorrect playback

Open a midi/karaoke file with multiple parts. I have attached the file I encountered this problem in.
Open the mixer.
hit Play.
Change an instrument to something else using the drop down in the Mixer. In my case, I changed Baritone Sax to Choir. instead of playing the Baritone Sax line as Choir, playback on that line stops while all other instruments continue. This may be normal and is not what I'm reporting as a bug.

While the score is still playing, change the instrument BACK to to the original instrument (In my case Baritone Sax) and just that the part will play from the beginning, while the rest of the parts continue playing from where they were.