Hey! I did run into the same issue (as I mentioned in another thread).
You are correct in your assessment of the issue. It is a weak link in this plate. 3 studs on the sliding part. One has the head shaved off to clear the plate. That's the one that breaks. It is indeed held only by a couple threads and a spot weld.
I spoke with GC and they recognized that this one stud is not very strong by design and said it has to be tightened with care and by hand.
They honored the warranty without issues though. I was worried I was gonna have to fight and argue that I didn't break it by over tightening but that wasn't the case. They sent me replacement parts right away via regular ground at no extra charge. I also asked for a spare one for the other side "just in case" so they sent me a pair.
I was a bit worried when I went to get my alignment done (since it has to be loosed/tightened) but I let the tech know and everything went smoothly.
I've since been to the track a few times without issues.
Anyways... I feel your pain. I installed those myself so I only wasted my own time and did not have to pay an installer again and again but either way it's a little disappointing and certainly unexpected coming from a company with such a good reputation. That and those plates aren't exactly cheap either... I'm glad I wasn't disappointed with their customer service.