Let me update my efforts with a bit of information:
1. Virtually all Harmon devices have identical hardware. In theory, *any* module can be flashed to any other module (Bespoke, NAV only, Entune with or without other apps, etc).
2. A process known as "authenticationService" is kicked off to verify the installation; if this process does not somehow agree that the software you are trying to update is unmodified (you can change minor things, but not the version, which is the big one), the authentication process returns an error and blocks the update.
With that being said, I have no visibility into this authentication process, and it's probably crossing some legal lines to start modifying it (if I can even get that far), so I'm halting efforts. Maybe someone with a bit more familiarity with the code will eventually step in, but since this is a low volume/specialty item, I don't see that happening
