I actually don't have a passenger riding in the front very often, but when I do, there is sometimes a loud "crack" sound when the front passenger door is closed. I don't know if it's metal hitting metal or glass hitting metal or what, but it can be a little startling to both the passenger and myself and a little embarrassing when I have to tell them that my supposedly nice car "doesn't usually do that". I haven't been able to tell by examining the door what is hitting what, and it doesn't happen most of the time. Does anyone know what this might be?