Nested Mail Merge cannot handle empty lists.
Workaround: Replace the empty list with null.
Merge field group in a single table cell causes it to replicate more times than expected.
Workaround: add a second column to the table and move the TableEnd/GroupEnd/EndGroup/RangeEnd merge field inside it.
Import/Export of specific documents sets style background color to black.
Workaround: do the following conversion of the document with the Document Processing libraries: originalRtf -> exportedDocx, exportedDocx -> finalRtf. After that processing, the finalRTF file will no longer reproduce the issue when exported.