We have Word documents as templates for DocMerge.
The merge produces DOCX files that Word cannot read.
Some versions of Word give a helpful error message that specifies an illegal character in word/document.xml
Unzipping the DOCX and viewing the XML file shows data from Sugar as just "&" rather than encoded "&" which is how ampersands look from the template itself.
This sounds like a problem that people must have already found and fixed.
If we change the "&" in Sugar to "and" and try the DocMerge, it works correctly and the document shows in Word.
If we then change back to "&" and try again, it again produces an "illegal" document