Looking at the pictures of the fuselage interior of the B737 door plug that blew out, looks like the attach points just didn't have fasteners installed. The attach points seem to be clean. Any NWguys have inside knowledge?
Reminds me of how I test fitted the insert for an arrowshaft pushrod and forgot to go back and epoxy it in. It worked fine for several years, but, you guessed it, two weeks before the Nats, it let go in a hard pullout.