type 4 clutch not releasing Options

[bangoos]

Hello fellow Porschephiles!

Installed a new clutch disk between two used but in good cond surfaces.
The flywheel surface appears near new and measures new according to specs in the Porsche "Technical Specifications" book that I have. The pressure plate surface also appears near new and is the type 215 Sachs. The disk is also Sachs and measures 10mm thickness. Pilot bearing is clean and well lubed. Input shaft is straight and true. There is no oil or grease on any of the surfaces inside the bell housing, on the back of the engine, or on any of the clutch parts. Side shift trans has new lube with all new seals. All shift rods and junctions are in excellent cond. Using Rennshift shifter. Trans shifted fine before switching to new disc.

Installed new clutch cable. Pedal bushings are good. Cable pulley is good. Cable adjusts well enough.
BUT!
clutch will not fully disengage, therefor no shifting can be done.

I removed the trans yesterday and swapped out the pressure plate while inspecting all surfaces and checking to make sure the pilot was not being jammed some way. Put it all back together, still cannot shift, clutch will not fully disengage; and with a better pressure plate installed this time, the shifting is even more difficult, as the plate is a bit better than the first one. Adjusting the cable to full tight has no effect. Setting it to 1" pedal play works the same as fully tightened cable, no pedal play. Stepping on the pedal makes the clutch slip, but does not fully disengage, no mater how the cable is adjusted.

Mega frustrating.
Is the disc too thick?, The clutch worked and shifted with the used disc in it. Old disc was about 9mm thick, thinner due to age ware. The new Sachs disc measures 10mm. I also have a rebuilt Sachs disc that measures 9.8mm, and several used discs measuring between 8.5 to 9.5mm.

OR?
Is the pressure plate faulty in some way.

Once again, the critical dimensions of the flywheel are correct for use with these parts. Of the above two possible faulty components, the pressure plate seems to me to be the culprit.
How can a pressure plate be faulty?
Warped surface
Scored surface from clamping onto the exposed rivets
faulty diaphragm spring, not levering the plate away from the disc far enough

Seems to me the only possible problem could be the last of the above three potential
problems. The second of which does not exist.

So it is really that I need a new pressure plate?
Can the diaphragm spring be wore out? bent around it's fulcrum ring? Incapable of levering the plate to free the disc?

Your comments are welcome.
Thank you!