When syntax highlighting for Basic code in help texts was implemented (revision d06c698b799e0e4ceaf3a3760c9589fe29dc29a9 ), a new element <bascode> has been introduced. But the doctype definition for the help files in xmlhelp.dtd has not been adapted.
Christian Lohmaier committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/contrib/dev-tools/commit/?id=5f231ff8263565988470f7fbedb90ff3a4883174 tdf#94057 - add support for bascode tag (preserve on roundtrip)
Christian Lohmaier committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=a14d38465c010b4feedfe6c2317a6eef59ffa09b tdf#94057 - add "bascode" element to xmlhelp dtd