Door rattle. Any ideas?

[A4DJ]

I noticed this starting to happen on 3 of 4 doors. No rattle when driving but when opening and closing the doors, there appears to be something slapping against what sounds like the window inside the door and also against the outside panel of the door. I pulled the door panel off today but don't have any adhesive to reattach the sound deadening material yet so I'm waiting to get some before I pull that off. Just wondering if anyone else has experienced this? I have a video of it but don't know how to post it from my phone.

[A4DJ]

Oh yeah, the Windows are currently down for pulling the panels, which is why I hear it hitting the window. When they're up, the sound isn't as loud and it only sounds like it's hitting the outside of the door.

[cobraBLACK]

I had a rattle in the front passenger door so replaced the window regulator. That fixed it.

[Alexztt]

I have seen on other vehicles the crash bar in the door become unglued from the skin causing a hollow sound when you close the door. We used some strong body shop adhesive to reattach the two. Just something to check

[jmcS4]

door handle covers loose???