Has anybody had any experience with this condition?
Can you drive the car without causing any damage?
If you've had it, how and what happened?

 

If it is carbon locked and stuck due to this, you will have low compression. The ATF treatment will probably help. I have a 1993 that it appears the spring has pushed past the apex seal causing it to appear collapsed into the rotor and stuck down.

Don't run the engine this way. If it does not unstick with the ATF treatment, it is time for a rebuild.

Tim