During WWI, the French deployed a really good field gun, Canon de 75 modèle 1897. Late at war, the US adopted this design as well and started manufacturing those guns at home.
Nevertheless, even with all the blueprints at their disposal, early American-manufactured 75s were inferior to their French counterparts. It took a personal visit of the senior French engineers in the US plants to correct various subtle flaws in the manufacturing process.
Documentation counts. The problem is a lot of insider and seemingly-common knowledge is never written down and is usually spread through word of mouth. Any sufficiently lengthy disruption means that knowledge is lost.
Some knowledge is hard to write down. Imagine trying to teach yourself karate from books only. It might be similar with some mechanical or artistic skills that are best taught in person.
Arguably, nowadays, with cheap recording devices everywhere, it is easier than before to produce comprehensive documentation even for such activities that are hard to write down.
Nevertheless, even with all the blueprints at their disposal, early American-manufactured 75s were inferior to their French counterparts. It took a personal visit of the senior French engineers in the US plants to correct various subtle flaws in the manufacturing process.
Experience counts.