Sure grip question

So how come when I tried to reassemble the axles with Green bearings the 2nd axle would not go in all the way? Once the buttons were removed, the axles went in all the way. These were stock axles with a Dr. Diff center section. And no, I am not a troll.

I've never been able to get the thrust pin in with green bearings either. I've done more than a few.