Are we sure the ITS rules in its.sch (especially the locNoteRule ones) are correct?
I’m getting syntax errors like “A location step was expected following the '/' or '//' token.” When trying to process them.

I’m certainly no XPath expert, but the “//::” parts look odd.

For example a rule like:

//xlf:file//::xlf:source[ancestor::xlf:file[not(@appliesTo)]/xlf:notes/xlf:note[@priority=1]] | //xlf:file[not(@appliesTo)]//::xlf:target[ancestor::xlf:file[not(@appliesTo)]/xlf:notes/xlf:note[@priority=1]]