I just added the file in MuseScore and ran MuseScore on the command line.
I got 
Debug: :/data/instruments.xml: xml read error at line 7214 col 46: Instrument

The file is valid XML, meaning there is no problem in the tag open/close matching. But for MuseScore, the file is not valid. We would need a XSD to have a more high level validation in another tool than MuseScore.