MuseScore generates unparseable MusicXML for ampersands in chord names
See the attached .mscz file, which includes the ampersand character ("&") in a chord name. When exporting this as MusicXML, the resulting XML (also attached here) cannot be parsed by an XML parser because the ampersand isn't escaped.
The solution is to escape the ampersand as "&" in the MusicXML. MuseScore already does this in other places (e.g., system text).