[Gaz64]

I had this trouble on one my cars a few years ago.
After verifying the hydraulics were fine, I pulled the transmission.
This was all new parts, steel flywheel, custom clutch, new special bolts. The pressure plate bolts were coming underdone.
They went back in with a lockwasher and red loctite. Issue solved. I could have had a pressure plate through the floor.
Gary