Friday before last I had a Helix clutch fitted to replace my original STi 6 clutch; it seemed okay, if a bit brutal, until Friday night when third gear suddenly decided it didn't always want to stay engaged when I let the clutch out. The stick "feels" normal but if I let the clutch out, 9 times out of 10 it pops out. If I hold the stick in position whilst I let the clutch out, I can't feel it press against my hand but in engages and stays engaged. I've also tried dipping the clutch in 3rd, and again most times it will pop out as I let the clutch pedal out again.

Anyone had similar or ideas as to what it's likely to be?