OT?? Thats right ON Topic.
The fact that it skips due to movement means it may be different than what i dealt with, but I'll give it a shot. I had someone ship me a non-functioning (skipped constantly) Alpine a few years ago, which I fiddled with and got working. You never know, have a read of this and see if it makes any sense. I wish I had taken pics, but once i was in there, it went so quick i didn't think to snap any shots.
It still works flawlessly to this day, even stuffed in the rear arm rest in the upright position.
Dave M