Is it the blade that spinning or is it maybe the gear spinning on the shaft?? I dont have a CX here to consult but isnt the upper gear the one that controls the lower rotors??? If it is (guessing again) I also think that gear is a pressed fit onto the shaft. Theres no way to tighten this 1. You need to replace the shaft and gear. Like a 10 dollar fix. Like I saidd Im just guessing here cuz I no longer have my CX. Anyone else wanna double check what im talking about plz?