This is why your door pops.
See that black-ish roller thing? It needs to be round, not grooved. When the door opens or closes the roller spins and falls into that groove making the door pop.
here's what you need.
I'm not sure if you'll be able to replace it without needing new hinge pins though. (the stock pins have to be cut to take them out, a real pain in the butt if you don't take the whole hinge off the car)
Just note that this won't really solve any door sagging problems if that's what you're looking to fix.

 

sweet!!

Thanks guys!

Will respond when completed.

-Ivan