As mentioned by Ignatz72 there is a recurring problem with the throw out bearings. I don't have one of these, mine is the older system. But the throw outs were made of metal and later plastic. They were multi piece and later they were a single piece design. The throw out bearing is inside the rear cover. It can expand with heat and can get stuck in the bore so I think this could cause the clutch spring to not release.
The parts fiche shows it as two pieces but if you buy a new one it is one piece.
I hope I got this right but I don't have one.