Earlier quoted context omitted.
The 737 fuselage is shipped from Spirit to Boeing without an interior. The door plugs are removed by Boeing during the interior installation. It is up to Boeing to reinstall them properly. https://news.ycombinator.com/item?id=38920716
We don't know whether the reason they are failing is due to an installation issue or not.
However, you are correct. Until the final NTSB report comes out, we don't know.