Percussion instrument Patch defaults incorrectly

I've been creating a marching band score, and when I open up the file, the percussion parts default to an incorrect voice when I select notes AND during playback.

For instance: all the notes in my Cymbals part become voiced as Flute notes, Snare voiced as trombone, Tenor drums voiced as some weird synth. I've been able to change the voices back to their correct ones in the Mixer (specifically the "Patch" dropdown menu). But when I hit save, close, and re-open the file, it's back to the incorrect voice.

I am led to believe this a Musescore 3 problem, as I have never faced this in 2. Any help would be appreciated.