Hi Will,
this is a well known error in the dbus-glib bindings. It should be fixed by now, but I am not sure if a release of it exists.can you confirm if this error was a general problem with the bindings or specific to NetworkManager? In the past or just recently? I want to excludethat it is caused by the documentation stuff in the introspection XML.
it is general error with the dbus-glib bindings. Meaning that all programs using dbus-glib and properties will have this problem.
Regards Marcel