Just gone thru the hydraulic system on my 1998 Spider because the pedal was sticking on it's way out about a third of the way from fully released. Honed and kitted both cylinders, solid bleed of system, all good. I also removed actuation arm on gearbox off it's spline and greased the removable bush. I marked which spline this came off and replaced it to the same. However if the arm is a spline or two out the pressure plate spring will not push the slave piston fully back which in turn will not push the master cylinder fully back which in turn will not push the pedal fully out. There are no return springs in the hydraulic cylinders, only a light spring in the slave to push it's piston out in the opposite direction, it all relies on the pressure plate.
My pedal when pulled out with my foot didnot drop back down like yours. I also removed the pedal off it's pivot shaft and found evidence of it binding, spaced it off with a thin nylon washer. the things brilliant now, but I don't think I really needed to do the work on the cylinders.
You could test the arm take up by putting a lever between the ball end of the slave and the actuator arm and see if there's any slack, theory is that if another person watches the pedal come fully out when you do the test, adjust the arm on it's splines.
Also when the pressure plate and thrust bearing were replaced, if they were of a different overall thickness this arm would have to be adjusted on the splines, did they do this?
I hope this helps.