Re: Drivers door "cracking sound"
If it's the same check strap unit as the 145, which it probably is, the fault, as others have said, is most likely to be a fracture of the bracket holding the assembly to the inside of the door. You may find that one of the screws holding it to the door is loose & that tightening it makes it a little bit quieter; that's a sure sign that it's broken.
It's a manufacturing problem which Alfa really should have sorted! The bracket is made from steel around 5mm thick, which is press-blanked & then bent to shape. Unfortunately there's a sharp corner right on the bend which forms a stress raiser, causing eventual failure. If it's left too long there's a danger the inner door where it mounts will crack.
The new part cost me (for a 145) around £16. Fitting's fairly straightforward.....as with any job inside a door, be prepared to lose a fair amount of skin off your hands!
Where are we going & why am I in this handcart?