@Siedlerchr There is something fishy in the pull request part of github/jabref
Even when signed in I can not comment any further. I have tested the files you provided. Obviously the [Formatter not found: CreateDocBook5Authors] and [Formatter not found: CreateDocBook5Editors] macros are not within reach of the export files. These are outside of the docbook5 layout files.
Regards
Bernhard