How to tighten door cover (photo)?
 

Ever since my mechanic worked on the window regulator, door cover (see arrow) is loose and makes annoying rattling noise when I drive. Before I take it back to the shop, is there a way I can re-tighten this cover? If so, please show me the steps. Thanks.

Most likely a clip broke and the mechanic just put it back together with a broken clip.

:iagree: You should be able to see if a clip is missing or broken and fix it without removing the entire door panel. To get better access carefully but firmly pry the bottom of panel out. The clips are press in clips that slide into slots on the door trim and press into the metal of the door frame.

Ditto what the others mentioned above...see item #23 (encircled numbers = hardware)...there's also an illustration of what the clip looks like in the inset index for the hardware that's illustrated in the diagram below. If you click the link, you can scroll down to the item nbr and get the BMW 11 digit part nbr which you can then either google "BMW xx xx x xxx xxx" (x = bmw part nbr digits) or check your local BMW dealerships parts dept for a price quote. They probably are about $1 ea & you can see in the part nbr index that there are approx six gray ones (#23) and two white ones (#22):

just checked it and the screw #23 is not in the slot(hole). tried pushing and tapping the trim to click it back in but still loose. any better idea?

Like it was pointed out to you before broken clip. The thing you call screw #23 is NOT a screw. It's a broken clip.

I see. So how do I pry it off safely and replace the clip?

I been working on mine all day...........check the support in the door.there are 8 clipps and 4 scews.