Export Errors - cannot export tracks to Wav or Mp3 successfully

Since the latest update, I cannot export tracks to Mp3 or Wav.

What I do:
Click File -> Export
Pick the tracks I want to use and the file format.
Set the file location and Enter.

What it SHOULD do:
Give me a separate track for each instrument that I can pull over to Studio One for mixing, etc.

What it IS doing since the update:
Gives me a separate track for each instrument - but each track actually contains a blend of multiple instruments, e.g., my Piano track has Piano AND Violincello and some Drum Kicks. Some of these tracks are garbled with clicks and audio stutters.

I've tried uninstalling and reinstalling. I've also tried downloading a fresh version of Musescore 4 on another computer and then opening it through the cloud storage. I didn't have any problems at all before this update.

Is anyone else experiencing the same glitches?
Does anyone have any other ideas?