You're not going to like this answer but I had something jammed in the interior I just swapped into my car, had to take the back seats out the car, and then used a torch to find something jammed in the mechanism and then stabbed that with a knife until it came out, then shake the seats about until it fell out
It was the only way I could think of to get the angle needed, turned out there were a few pieces of a kids toy and a sweet wrapper stuck right at the back!
Works fine again now though, just a pain in the ***** having to remove the rear seats after I'd just put them back in first time in two months :o