The clops are called Blow Out clips, and were added to the G-bodies because at highway speed the movement of air across the windows will cause them to pull away from the gasket.
Another common problem ( that causes issues with this clip) is the nylon "guide" that is riveted to the lower rear section of the glass. These tend to get broken over time ( people using the window to close the door). This guide fits into a metal spike that protrudes down into the door about 3 inches from the top of the door, so the last three inches of the up movement is guided by this rod and guide. If the guide is bad, you will never get the window to adjust and close properly.
You can test to see if this is broken by rolling up the window with the door open. Grab the window and move it in/out ( like you were going to close or open the door). If there is any play between the window and the door( mine would move maybe 1-2 inches at the top of the glass before the door started to move), then the guide is bad.