Coded New Vessel Considered as a Repair

What does ASME say about field repairs?

Send it back to the shop that made it wrong. Let them fix it.

I know, that takes too long.

We had a saying back where I used to work on government satellites.

There's never enough time to do it right in the first place, but always enough time to re-work it.

Also, it won't be "fully PWHT" after it is welded, will it?

There are too many unknowns. You need to get your pressure vessel insurer, company pressure vessel engineer, and maybe the fabricator together and make a decision.

All testing and certification is void once the welding starts, as the vessel will no longer correspond with the drawing that was filed with the insurers before it was assessed for burst indemnity insurance. So, whatever testing will need doing again, after the drawings have been done again, and after the insurance assessment of the redesign has been done again.

Whatever numpty carried out the Customer Factory Acceptance Test needs despatching to Mars on a one-way ticket.

Let us talk technically here , the answer to your question is nicely given in detail in ASME Sect 8 Div. 1 , UW 40 (a)(5). in brief you PWHT a circumferential band containing the pad plate as detailed in ASME

...however, if the plate were attached with an epoxy-resin adhesive instead, the vessel's metallurgy would be unaffected and no retesting or certification would become necessary...

I think Vessel made by rubber so no cooking required.