Amazing and my further question: What degree of scientific discipline and/or stubborness would it take for the Bell Labs folks to actually get to the bottom of this and finally trace it back to the copper and the door knobs?
The motivation seems easy though, wafers cost a lot of money! No one wants to see low yields. They are constantly testing and measuring everything to try and find root causes. Look at some of these diagrams if something can be isolated they try to do it.