When generating service artifacts with wsimport, any classes pre-generated using xjc still have ObjectFactories generated even though they're already in the xjc-generated jar. These ObjectFactories can be generated differently from each other, though they're referencing the same underlying type (i.e. nillable).
To work around this issue, the duplicates need to be deleted at build time, which isn't a maintainable approach long-term.
Ideally, wsimport should not generate any ObjectFactories or perhaps methods in the ObjectFactory which are already present in the xjc-built jar. Perhaps the episode file can be of some assitance here, since wsimport is smart enough not to create the .java files.