Have you checked the air gap, or have you checked the spring height on them and checked the engagement rpm? Some of the spring set screws could have backed out and lowered your engagement rpm too much, causing the clutch to try to stay engaged on you like your experiencing. Another thing is if you dont maintain the clutches every week, pull them off and check the needle bearing in the driver, those bearings need to be cleaned and lubed regularly or they can get dirty and try to seize up on you. I had a 2 disc horstman reaper clutch lock up on me this past weekend, i almost didnt get it off the crankshaft of the engine, when i did get it off i realized that the needle bearing in the driver had seized up and was keeping the driver from turning freely on the shaft, causing the clutch to stay engaged and not working properly. If i had pulled it off and lubed it properly in the last few weeks i would not have had that problem, but i neglected it because i have been busy with working and havent had the time. Now ill be taking the clutch off after each day of racing and cleaning it completely and relube the bearing and reassemble for the next weeks races.