On examining slave more what we find is the stem of release bearing is made of plastic.
On the bottom of it is a thin metal end cap that prevents the inner grooves ends from hitting slave stem and also prevents bearing stem from tilting.
This end cap broke, fell off and now lays at the bottom where seal to fluid in base is.
This then causes bearing to tilt, jam against slave base so it cannot move smoothly and then grind grooves into that base stem.