Master/slave clutch mistery

[goldNSX]

I've changed the clutch master recently and now the clutch seems not to fully disengage in very seldom cases, like 1 out of 1000. It happened about 5 times so far and ended in a nice sound from the gearbox, always from spirited 1st to 2nd. There is no air in the system and this hasn't happened before (with the old master). There is also no leak and the fluid level is perfect. It just acts like some owners reported by the clutch pedal fell through but never happened for the next 20k or so (a rare event but of no concern).

I know I can and will change the slave too. But my question is if it's more likely a bad (new) master or a bad slave not coping up with the new master? Did anybody get a bad new master?