clutch fork pivot

My father has an '87 convertible with the 4+3 transmission, and has had a clutch problem for a few years now. the clutch has been changed twice, and feels weak, and engages with the slightest movement of the pedal, and grinds when going into reverse and first. Could the fork pivot cause this problem, or could it be a bent clutch fork? the clutch has actually been changed twice, and the release bearing both times. As well the clutch master cylinder and slave cylinder are brand new. Can someone give us a clue? thanks.