I had this problem where I bought a bare door and fifted everything. I tried for hours and gave up in the end. I bought another complete door and sold the other one as a bare door.
A few weeks later my sister in law had a window smashed at work and I had a window so I fitted it for her. Same thing! Tried again, nothing I did made any difference. I temporarily left it and guided it up with my hand so it was shut properly. 2 days later it shattered when she was driving. Now unlike the first one, nothing had moved. Just inserted a new window in and it clipped into place. She had autoglass come and do it and it was fine.
I am at a total loss as to why this happens. It makes no sense.