I found another potential workaround that seems to be helping. This is for MacOS:
Open soundtracks folder with open $TMPDIR in Terminal
Locate soundtrack file that isn’t working or use the XML file to find which soundtracks are used for which projects
Replace the soundtrack file for the video you’re working on with a .wav file of the same name. I used Logic to make the replacement since I noticed that one of the soundtracks wouldn’t play at all, even from the finder.
Should work after restarting Dorico, just make sure that you’ve removed the original and replaced it with a file of the exact same name. The new one will be appended with a -1 automatically if you try to put both in the same folder concurrently.