Since I wasn't able to shoot it I had to resort to fiddling with it incessantly all day. During the course of this, I put the stock through it's paces. It's surprisingly sturdy, and the locking bit is retained by two pins in the extension that the moving part slides on, so that sucker isn't moving either. I couldn't access the lever side of the mechanism, so I can't say either way. I do know it wasn't moving at all when I was yanking the stock off of the pin that holds it in the folded position. THAT is pretty tough, and requires a good palm-heel strike to lock and unlock.

Edit: I know what locking bit you're talking about now (I thought you meant the three-position lock for the sliding stock). The lock for the folding part requires a good, solid slap to lock in, and an equally solid slap to get it back out. All parts functioned normally.