Years ago on a 1971 spit, I put a remanufactured clutch disc in and it would not disengage. The problem turned out to be the aftermarket disc was too thick to disengage, caused probably from being poorly remanufactured “new.” I guess it is like rebuilding brake shoes sometimes they are too fat. Anyways the cure was to burn some of the newness off the cheap disc. I got the car running and drove it around for some time forcing the shifter some (ick) and disc wore down that little fuzz and shifted fine.
During this whole fiasco someone told me to put a temporary extension on the slave cylinder rod or get a slightly longer rod for break in of the cheap disc.
steve