Except for on VAG vehicles, which had been brought up by ANO and which I mentioned in my response it is anything but a high probability although there is a high probability that the garage will say it is, may even think it is and don't really care as long as it can become a clutch and DMF change at the same time as its false economy (agreed) not to.

If there is no leakage of fluid then its 100% not the CSC on any car, a failing master cylinder can exhibit the symptom without fluid loss and in that instance would be the main suspect on any car, it's sensible to change that first as its a relativeky cheap and easy job not involving pulling out the transmission.

If like me that did not work or only gave a temporary reprieve (the system bleeding) then its gearbox out, change of clutch, DMF and CSC, with the problem now gone most would deduce it was the CSC, mine was as dry as a bone so I did a forensic examination and was able to prove what I had already deduced/suspected that the O ring joint was drawing in air but not leaking fluid.

My motive was not to be pedantic but to avoid anyone being misled and having a very expensive job done by the garage only to find the problem comes back after a week or so, this is being reported more and more frequently on VAG forums.