Obviously the NTSB report is not finalized, but I think we can rule out metallurgy. Even just from the photos you can see that the tabs in the airplane that th

Obviously the NTSB report is not finalized, but I think we can rule out metallurgy. Even just from the photos you can see that the tabs in the airplane that the door plug rides up against and the corresponding tabs on the door (even though it fell out of the airplane) are still intact. The only other faulty metallurgy issues remaining would be if certain bolts that have not yet been found had failed. The likelihood of that is extremely low given how new the plane is, and there would be evidence of wear on the corresponding parts, which has not been reported. This pretty much guarantees some level of faulty assembly with incorrectly torqued or (most likely) missing bolts. Very much the sort of accident for which aerospace has a process to prevent.