The door plug could also be spun as a supplier issues. Ultimately this points to poor supplier management at Boeing. Boeing realizes this, and is taking steps to address it including purchasing Spirit.
Did you read the whistle blower commentary on internal notes on the plane that had the door plug blowout? It wasn't a supplier issue: the people inside the factory had an off-the-books message board that directly discussed what happened on that plane, and it was precisely because the Boeing employees that removed the door failed to record the door removal in the official logs that the failure to properly reattach the bolts was not detected. Door removal is one of the activities that would have required a reinspection. It was Boeing's fault through and through.