i have the same problem with excedy stage 1 too, its disengage really high, especially in hot temperature, i was told that it may caused my the clutch's master and slave cyclinder gets old, and since the spring rate of the clutch is different then the OEM one, it may cause you a problem because the fluid can't transfer efficiently. there is not much part for the clutch system so it might be it. I want to change mine but my financial situation didnt allow me to.
i may wrong, if so correct me.