Shaft nut gone
 

I had my adjustable shocks rebuilt. I installed them and drove the car 848 miles. At that time, by chance, I noticed that the adjustment knob had come completely off the shock shaft (rear driverside shock). It was sitting in the area where the strut tower brace mounts to the body.
I take the shock out of the car and notice that the nut that holds the top of the spring assembly onto the shaft of the shock is gone. Just plain gone, no where to be found.
The shock had shifted so as to pinch the adjustment rod (which sticks out above the shock shaft), against the body, where the shaft of the shock comes through. It pinched the adjustment rod to the point where it almost severed it.

WTF! How the hell does that nut just disappear? We could not have forgotten to put it on when we compressed the spring onto the shock. If it was not in place, the spring would have just come off as we loosened the coil spring compressor. When I took the shock out the spring just came right off the shock.

I'm completely baffled as to how this could happen. Could the nut have split in two? Has anyone ever experienced this?

Most likely it was not tighten enough, since it did it after re-installing the parts, and only one did it.

Many original washers supplied with Ground Control suspensions have failed by splitting in half. Happened to me, one totally failed and a few other were cracked. Their new ones are twice as thick.

Yeah, my thought was the nut may have split too. I wonder if the nut should be grade 8?

The shocks are Bilstein. I had two rebuilt because a local shop snapped off the top half of the threads on the shaft due to over tightening when using double nuts.
One driverside front and one driver side rear. So far, the front one is holding tight.

I would not use that shop again because they are not professional.
Over-tightening is an act of ignorance.