See http://musicbrainz.org/edit/21327190 where I encountered this problem. Release and release group are okay, but tracks and recordings are not. Those two people happened not to be in the database already, but that doesn't seem to be the problem as I just checked to see if that behaviour also occurs with known artists, and it does.

I hope this is the right place to report and complain. I don't know if it's the plug-in's fault or Picard's or the server's.