As in my original post, I put the original 100 series side folder back on and the stock still wobbles. Its not as pronounced but the whole locking mechanism is definitely moving in the receiver.
I only have a sample of one, ie my gun so this is why i'm asking here so as to make sure that my expectations are not unrealistic. My buddy has a 107FR and he told me that his polymer side folder is 100% rock solid. The hinge mechanism does not move AT ALL.
A couple points to add. The wobble is not coming from the hinge itself. The pin is tight and the stock fits well in its hinge. I can move the stock up and down a little bit in that hinge but I would say that's probably normal since the stock has to rotate on that axis. The wobble itself is coming from when the stock is locked and the claw hook, "barn" door portion of the assembly and the internal locking mechanism itself, starts to move around inside of the receiver.
There are no visible cracks, bends etc. I was wondering if there was a way to "tighten" the mechanism? Just by looking at it, it does not appear so.
I figured that given the nature of the metal and its design, over time it would fatigue and loosen up. From what you guys are telling me, this is not the case. I have zero clue what happened when it went back to PSA so I'm guessing it was either dropped or damaged in transit. Who knows.