Very poor weld inspection, both robots and hand welders get their welds inspected. That wasn't welded professionally on either side, the weld on the side that had the tiny bit of contact at the lower corner, was a rather poor stick weld attempt ..... that should have been pick up on the predelivery inspection, even if it was completely missed at the factory ......
My guess is someone tried to fix it without removing it from the vehicle and they could only get partial access from one side. They deliberately avoided excess heat where the rubber bush was, so, even though the weld might have looked ok, it only penetrated one piece of the joint, and barely at that ..... you can see on the poorly welded side, the black paint sprayed in through the gap during assembly
T1 Terry