That noise may have been the spring in the regulator. In any event, I'd check the following;
1. Make sure the window is not binding on the sides of the cap.
2. Make sure that the window is in both door side tracks.
3 Make sure the regulator arms are properly engaged in the window support tracks. They could be gummed up with old grese and dirt so check that.
4. It may be necessary to remove the window and pull the regulator out so you can see if there is a mechanical problem with it. While out plug in the motor lead and see if the regulator functions properly without the window.
That's all I can think of right off the top of my head.
Good luck,

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