Happened to me, twice, so now I have a new stock. The internal part of the button has a tendency to ride up on the notches on the RET. Once it slips and collapses, the notches get hogged out and it will never work right again.
Other than that, nice stock.
I consider my “story of teflon” to be a first hand account, as did the person in my carbine class. That was years ago, and if they are still loose like that then there is a problem.
One of my friends has had to put teflon tape on not one but two different UBR stocks on two different lowers (RRA and I think DS) to eliminate wiggle.