V50 G/box : V50 2.0D mmt6 clutch hydraulic issue/mystery

[Easy]

I have a 2005 V50 2.0D with a six-speed manual. All was good, until the clutch slave cylinder developed a leak.

Car spec's:
V50 2.0D
Model year: 2005
Engine type: D4204T
Transmission type: MMT6

So, I spent some time on the internet and decided that it was safest to have everything replaced at once.

1st garage visit, replaced: Dual Mass Fly-wheel, friction plate, pressure plate, seals, slave cylinder and master cylinder.

After picking-up the car it soon became evident that the clutch was not bled properly, or so it seemed. After a couple of weeks and several bleeding sessions (carried those out myself), I concluded that it must have a leak in the hydraulics. So back to the garage ...

2nd garage visit, replaced: rubber seal between the hydraulic hose and master cylinder. (droplet of brake fluid noticed on the connection between master & hose)
3rd garage visit, replaced: all rubber seals in the hydraulic hose and the ones connecting to the cylinders. (droplet of brake fluid noticed on the connection between master & hose)
4th garage visit, replaced: nothing (droplet noticed again; seal removed, inspected and reinstalled)
5th garage visit, replaced: master cylinder (note: this is the 2nd new master cylinder, of course the issue remained)
6th garage visit, replaced: complete hydraulic hose assembly and friction plate (friction plate was soaked with brake fluid, resulting in clutch-slip)

Picked the car up today, fairly quickly noticed a changing point of engagement, it goes back and forth (depending on frequency of clutch use it engages at the beginning or the end of the stroke). This is the initial symptom before serious 'sticking' .... so the car is back at the garage (for the 7th time!!!!).

Anyone got any idea on a possible root-cause?
Because I am pretty sure that the garage mechanics are out of ideas; and, so am I.
Thanks in advance!