WAV export seems inconsistent

I am using WAV files to export MUSEscore to my DAW. When I export "violins" as a separate WAV file, it comes through nicely and, as I would expect, as simply the violin track. However, when I export "clarinet", it disconcertingly includes other tracks from MUSEscore: piano, voice, and contrabass. I can't seem to get an isolated clarinet wave file. I'd appreciate any help you can offer here. Thanks.