In a situation where something that severe (and malicious) is found, what would even be the short-term response? Are the management of the plant completely replaced?
Well, falsification of certificates seems to be quite common by nuclear subcontractors, and depending of the number of alternative shops able to do (kind of) the same thing (minus or plus correct quality...) those who falsify stuff might get away with a mere slap on the wrist and safety authorities telling them that it is bad, don't do it again.