One of the cross braces (steel tubing) cracked and snapped on mine (a 96) then the drive cable/spring popped out and got caught in the works.
The only way I found the problem was to pull the seat out, turn it upside down and even then I had to use a flashlight, it was really tight in there.
I got lucky and was able to free the drive cable. Then I stuck a piece of all thread all the way through the tubing cross brace, then put (super glued) a couple of nuts on the ends of the all thread. I spot welded the break back together just as insurance.
May be related to your issue or it may not, but stuff like this tends to fail regularly (repeats) at the same spots. Like the side braces for the seat back snapping off on SJ and early XJ.