Hi Michael,
It's possible this is a bug in JMatch, in which case, if you can provide details of exactly what you were doing when you triggered the bug, I can try to reproduce it. But more likely it's due to running on Windows ARM (which didn't exist when HotPot was created, and sometimes requires applications to be specially compiled for it), and/or Parallels, which is a virtual-machine hosting environment.
If you've been happily using Hot Potatoes for a while with this setup and haven't seen any problems, though, then there's a greater chance that it's a JMatch bug and we need to figure out how to cause it so I can fix it.
Cheers,
Martin