My Omnifi DMS-1 complained when opening any media file, so I made a couple of random changes to the SOAP reply
First, I changed the charset reporting from "utf-8" to UTF-8
This seems completely benign
Second, I removed the xml header from the SOAP reply:
<?xml version=\"1.0\" encoding=\"utf-8\"?>
I guessed at both of these changes by looking at the output of mediatomb which did work and comparing that with minidlna which didn't.