Possible for the stamped steel clutch fork to be letting loose.
That is the part that the slave cyl rod pushes on which is attatched to the throw out bearing that pushes on the fingers of the pressure plate.
It is not unheard of for fork to wear a hole in them after heaps of miles unlubricated

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97 e300d, 78 300Dt, 95 E300d, 94 E320 estate