Regressions related to eg. this work: https://wiki.documentfoundation.org/Development/GSoC/Successfully_Implemented_Ideas#Implementing_legacy_SAX_parser_Interface_with_FastParser https://lists.freedesktop.org/archives/libreoffice/2017-August/078392.html But this was more extensive work, so also more generally, any regressions originating from switching to XFastParser over the years.