Too short clutch fork?

I'm guessing even though you are trying to install the fork onto the pivot and the release bearing at the same time, one bearing clip is going easier and further than the other. May be causing the fork to tip up or down on the pivot and one side to slip off the bearing clip. Needs to go on straight and equal at all three points. Try again. If it's the correct stuff it should not separate once installed within the designed travel.