Slipping Clutch on Ducati Monster 600?

[ducati-mad]

I have recenty bought a secondhand m600, and found the clutch to slip after a few minutes running.
When cold it had normal play on the clutch lever but as it warmed up this reduced to nothing!
It was as though the hydaulic system was pumping up when warm. I decided to fully drain the system and look at all the parts involved. Upon inspection the clutch lever / reservoir assembly had a defect. The fluid return hole just infront of the seal which "vents" the fluid to the reservoir as the engine gets warm and stops it pressurising the system was missing! i.e. mine had one hole where there are normally two.
This motorcycle had never worked properly in it's 7 years and five thousand miles!
I drilled a 3mm hole just in front of the seal from master cylinder to reservoir, re-assembled, filled with fluid, bled the system, and headed out. Perfect.
Just thought I'd post this as one of you out there may have had this bike and wondered why the clutch slipped all the time. I must admit to being baffled that this wasn't picked up in one of the many services the bike had had.