I ran into that problem with mine. It must have loosened somewhere because I was able to eventually guide it in by hand, while the DW held the button. Since it was under warranty, I brought it to them and had them tighten up whatever it was that was loose.
I'm afraid I don't know exactly what it is they tightened, but check all the bolts, pins, and whatnot to see if anything's out of whack.
There's no use crying over spilled milk, unless it's on your keyboard.