Do you think it will be "purity" or understanding material variance/specific impurity?
It reminds me of Fogbank, the nuke material claimed to be "so secret they forgot how to make it." Part of the story of manufacturing difficulty was due to increased purity of modern materials/processes.
In a bizarre twist, the new production facility and reverse-engineered production process yielded a version of Fogbank that was of a higher purity than it had been in the past, according to the article. The problem, however, was that for Fogbank to work as intended in existing warhead designs, that previous level of impurity was actually essential. NNSA had to revise the process to ensure the final product was just as impure.
https://www.thedrive.com/the-war-zone/32867/fogbank-is-myste...