After completely removing the sliding load floor from the rear cargo area and turning it upside down, I was able to see what I thought was a set screw in the side of the body where the bushing/bearing was fitted.
As it turned out it was a ROLL PIN
that had worked its way out. Re-fitted the bushing/bearing and tapped the roll pin back in with a dose of Loctite 222 for good measure and we're back in business with one of my favorite features of my E53
Mike