Mark,

The check arm swings freely in some open space behind, and above the jack storage area. I know this because I have Tone's door popper installed and I ran the wires for the solenoid up through that area and through the rubber boot to the back door. One day the popper stopped working and I finally found the problem was that the wire to the solenoid had gotten pinched and cut. The rear door check arm had pinched the wire against a metal "bulk head" back above the jack. Had to re-run the solenoid wire so it didn't go through that area again.

I have to say, that IS a very strange part to break.