It doesn't matter who your supplier is, if you fastidiously check their work.
At that point it takes such a team that you might as well bring production in house. There's inherent trust in your supplier when you outsource.
Or don't squeeze everything impossible out of them. There is efficiency and then there demands that means corners will get cut or not cut when metal working is really needed.
But also the only core part of the fuselage they make are the wings of the A220 family.