I'm going to venture a guess that your clutch fork is sitting at a steep angle when it's on the throwout bearing, allowing the fork to slide off of the pivot ball when you push on the linkage? A picture of it installed would help us understand the problem. Just a guess, but you may need to get an adjustable pivot ball bolt to let you move that pivot point closer to the engine, flattening the clutch fork angle? Are you sure you've got the inside part of the fork on the throwout bearing right? https://video.search.yahoo.com/yhs/s...2&action=click

If that doesn't make sense post some pictures.