While removing my steering box for R&R, I disconnected the steering coupling. No problem in the process. When dismantling the coupler I discovered that one of the shoes inside the coupler was broken. All the other parts, including the coupler itself, seem fine (photo attached). I do have a coupling rebuild kit, so all the guts of the coupler will be replaced.

A little history:
The car, '68 RR was originally a manual steering car. One of the previous owners converted it to power steering so I know the coupling was off at some point in the cars life.

What may have caused this?
I want to make sure this doesn't happen again.

Thanks
Frank