I ended up in the InvocationTargetException when I did this:
(a) Join firstname.lastname@example.org from phoneA
(b) Join email@example.com from phoneB.
(c) phoneA and phoneB both leave the conference.
(d) phoneA tries to join the conference again, but ends up in the exception. I
also see "InvocationTargetException" sometimes during __addParticipant
Once this starts coming, it requires the SailFin to be restarted.