Happened to me as well, it was stuck slightly below the spot above the CD ramp where balls are locked for one or two seconds when you shoot over the ramp. I was able to resolve that through nudging, however.
Also, it happened to me twice that a ball would get "stuck" when the CD ramp was spinning on the ramp itself. The ball then jiggled around the left part of the ramp and was torn between gravity and friction, so to speak. This could also be resolved thorugh nudging, but not so easily.