End Limits Activated?

After initial install, our unit traveled up and down full length three - four times. On the next trial run, the chair traveled three (3) inches and stopped. Did this several times. It will not move unless you crank it manually a couple of inches, then it stops again.

Ok, I know the problem, but not sure how to get at it.

The upper end stop ( the longer plastic one ) has broken off a piece and wedged itself .. traveling down the track with the chair.

How do I get the piece out??