lxml.etree.XMLSyntaxError: Opening and ending tag mismatch: groupChrPr line xxxx and groupChr...

[yhjiang15]

in __init__.py
line 787 and 750 should be:
'</m:groupChrPr>'
not
'</m:groupChr>'

[USSX-Hares]

The error is being triggered with vector operator:

\vec{AB}