MK7 Clutch Pedal Dropping.

Hi all

I'm looking for some advice with my Transit clutch.
It had a recon engine in it around a year back. It had a new clutch kit fitted at the time.

If I'm just pushing the pedal endlessly the pedal goes down and returns as it should.
Driving the vehicle up the box the clutch and pedal behaves normally.
Going back down the box from 6th to 2nd say, with each clutch pedal push down, the pedal does not return all the way back up.
When this happens the clutch is half engaged as you cannot select a gear and the engine revs up. 
If I put my toes under the pedal and help it back up it's fine (until the next time).

Despite there being no fluid like, the garage said it was the master cylinder so that was done.
Then they changed the slave cyclinder as the fault was still there.

The only other thing I'm thinking is if the pressure plate is worn and the springs are not forcing the release bearing back
but then I can't work out why the pedal doesn't stay down all the time.

I suppose I could fit a spring to the pedal but I want to know what's wrong with it.

Any help would be greatly appreciated.  I'm losing the will to live!!!!!

Cheers

Karl