You mean it's pinned I'm guessing, and the pin is what you can see from what I am picturing, photos?
Will look to see if the DoubleTrack is welded and pinned, as I'm not 100% sure, but would imagine that this is it.
As for why it's doing that, I couldn't say, but it must either have been hit hard and damaged or its faulty.
Get on the blower to Sun if this is the case