Hah I am no expert but I do know Primero has very highly...

Hah I am no expert but I do know Primero has very highly acclaimed engineers and that NRW’s RCR heat treatment facility in Welshpool has a very high reputation as well, with people there who know exactly what specifications they need.
To quote further from today’s HZR announcement it seems there is a manufacturing flaw with the shell;

… “Hazer has been advised that a manufacturing flaw has been identified in the Hazer reactor vessel currently waiting for heat treatment in China. ​

Quality assurance and non-destructive testing activities carried out over the last 48 hours have yesterday confirmed the presence of the manufacturing flaw and identified further areas of concern. ​

As a result of the flaw identified, the reactor shell has been deemed unsuitable and will require remedial manufacturing actions before it can be certified and accepted for dispatch….”​

… to me that indicates it’s not a design fault.
maybe someone over there ignored the new specifications?
And bringing NRW’s integrated design services advantages into this, maybe it was the RCR heat treatment guys working with Primero after the acquisition who actually recommended the changes to the reactor build?

But I’m prone to idle fancies
(And I did sell a little clutch of shares over there today in case HZR falls lower … but NOT here! )

cheers and I hope you do sleep well!