[Excaliber]

I don't think bleeding the slave is the answer here, my guess is you have already done that enough. It's very easy to get the air out of this type of system. The slave piston is moving out because of it's internal spring, that's OK. You need an external spring to overcome the natural and expected movement of the slave piston.

If your existing return spring is not able to seat the slave piston and provide some clearance on the pressure plate fingers the spring is not strong enough, or is not mounted correctly. There is no reason other than the internal spring for your slave piston to move toward the end of it's stroke. More bleeding likely won't have anything to do with this issue, I think it's a red herring.