A common trick to relieve the constant worry of set screws backing out, is to put a short piece of heat-shrink tubing around the bell of the cvd.
Also, if they were chrome plated, then there is always a risk of flashing left in holes, and on edges. One should make it a practice to always check parts for fit and finish. I would bet that a pass with the right size bit, or even de-burring with a blade from an X-acto would have loosened that pin up.
Another common trick for cvds is to use a short piece of the appropriate size allen wrench as a pin. It seems to be stronger, and it's got flat edges for the set screw to seat into.
As for the limiting of the suspension travel...When you run dogbones, there can be 'clearance' on both ends of the bone to facilitate full articulation of the suspension arm. When you capture one end of the bone, then you may have to limit the articulation...That is just logic, and has nothing to do with MIP, or anybody else that makes them.
I agree with you in the notion that when you buy expensive aftermarket stuff, it should make your ride better. But law of averages says that there are going to be a couple of bad ones that slip through. Luck of the draw, and you got it this time.[:@] Better luck next time.