When the GUI is used to create a membership in an association. The membership role includes at least one bogus property whose URI is actually a file URL. This can be seen by editing the role object and choosing "Raw Statements With This Resource as Subject".
See the attached file with output from that request.
A side effect of this problem is that it breaks the Linked Open Data response for the Person or the association, if the LOD is in RDF/XML format.