My quaife was an absolute nightmare getting the shaft cups out of the diff. It's more than likely just a really stiff fitment, as Phil said above I also had to beat the death out of my shaft to remove it from the box, to the point where I was certain I was going to damage the aluminium gearbox case. Best way to tell if it's the clip is pull the shaft out and remove the clip, if the shaft slides all the way in then you know it's the clip causing your problem