Seems that it's not being seated all the way. It should click. At the end you are pushing in should have a circlip

 

 

 

Something is REALLY wrong. There should not be that much tension pulling on the half-shaft. Check all your dimensions, as the only thing I can think would cause the joint being torn apart is some kind of frame damage, or replacement control arms that were too long for the car.

Jose

 

that's what happens when you lower an xi. you either need to raise the car up a bit, to keep the joint in its happy place, or get a custom axle made with a longer shaft.