Knocking when driver door is shut

[lsheltonnn]

It's a 3door 2010 a3.
when shutting off/side front door, there's an audible knocking from the underneath/rear of the car.
even when using little force (little enough to not even latch) the knocking is audible.

I suspect the door has dropped a little / or is too high and will need to be adjusted; however, just posting to see if anyone else has this problem or would know why the knocking is coming from the rear of the car.

Thanks in advance

 

[prt57]

Sometimes sounds can appear to come from a particular location.
To begin with, have someone close door whilst you pinpoint the origin of the noise.
As far as I am aware there is no reason for a knocking noise from the underside or the rear when the door is closed unless something is loose and the jolt is making it move.