Service bulletin #45 has the owner replacing the elevator bell-crank to push rode bolt every 50 hours.  Not that easy to get to; (kinda tight back there, and tough on the fabric to get the old one out and new one in).   Have you Model I, II and III owners been doing this?  Still seems odd to have had two failures, though initially it was spec'd as a screw (AN23-15A) vice the now AN3-15 so maybe alleviates the concern (not sure if the chemistry is any different)?  I assume the Model IV has a different arrangement?