No kidding that it wants the actual case it came in for this update!
Before I found this post, I'd tried and failed to update it in my main case. So with your tip (thank you!) I tried it with a proper Moog 60hp case. I dug around in my gear and found one, then mounted my subharmonicon in it. The update still failed, (stuck on the third sysex file, lights just do the "updating" sequence forever. After rebooting, it's still stuck on step 1.
So... I flipped the 60hp case over to double check, and sure enough it was the case my DFAM case in, not the one the subharmonicon came in. So I dug around AGAIN and found the actual subharmonicon 60hp case, re-mounted it and then the update succeeded.
Again, thank you for figuring this out!!!