Pics would be handy.....Sounds like the "drive arm" isn't sitting correctly, and could have slipped forward, check it is sitting linear, also, throw an elastic band from one securing lug (the screws on the side) up over the top of the a-bar, and onto the other screw, like a saddle, see if this helps and check the rear pivot of the a-bar is nice and tight, wth not much "play"...Have you had it for long....?