Clutch problem, sometimes drops

Hi all, slight issue with my 300tdi, sometimes the clutch pedal sits low, if u pull it back up it will operate normally, I've read about the clutch fork bending but if that has happened surly it will be down all the time, iv had a similar issue before on another car and it turned out to be the clutch master cylinder. Any ideas guys? Fluids all topped up

The pivot ball might be getting ready to bust through the clutch fork. Happened to mine a few weeks ago.