I believe that the additional holes for the "line based" raising/lowering system may be the culprit. There are actually two more holes in the rudder blade in that system rather than with the "rod" system. One hole drilled for the stopper knot and one hole drilled 90 degrees to that so that the line can be fed out of the rudder, up the stock and to the jam cleat. These holes are located just below the bottom of the rudder stock - where the loads would be quite high. I believe the newest rudder blades are solid core construction, instead of having some internal foam. My rudder blades were produced right after the US switch from "rods" to "lines", so they may not have been suited to that change.

BTW, Vectorworks as been great about sharing improvements and open to frank discussion about the product. I sincerely believe they are close to getting all the right pieces in place. My only problems have been the rudder blades and my problems may be more related to the timing of my boat delivery than anything else.