It's possible to have a bad weld - but pretty unlikely. These are all welded by a robot with pretty sophisticated electronics that monitor the welds. If you ever get a chance to see one in action - it's pretty amazing. I'm also in the camp of it probably being paint defect, but I'm curious to know. Any chance you could take some better pictures?
Ah I couldn't tell by the picture very well and thought the actual weld was cracked. So this is a whole different issue entirely, my bad.