I dunno if anyone else has had this problem, but the top plastic slider piece on my guide always develops a crack directly on top of the front screw hole (with the crack running parallel to the screw). I dunno if it's from me over-tightening the bolts (which I'm pretty careful not to do), or if it's just a weak piece of plastic that's prone to cracking. This is the 2nd time it's happened to me, and it's really a pain in the ass. The crack isn't so bad that the top slider falls off, but it makes me wonder how securely it's being held on. Anybody else had this problem?