Sorry to bump such an old topic. Today this funny click started on my 2005 156 (RHD), sounds like a gun shot too. It seems to be coming from around the rear right side.
Today I removed the aftermarket stereo from its column as I was fixing some cabling. Then I tried locking the car from inside and it locked, but there was this strange sound each time. At first I thought that it had something to do with the stereo, so I removed everything, and the problem was still there.
When the locks go down, during the click the locks move a bit upwards.
I was trying to get rid of another sound (which apparently is the loose gas tank cap) and now I have this new sound lol, call it Alfa Romeo character?
Any ideas please?