Reading the tear-down is rather entertaining in its own right (in a techno-nerdy sort of way) but the thoroughness of the description of the process and what it finds is very interesting. If you don't want the detail go to the conclusion at the end for the "executive overview".
https://www.lensrentals.com/blog/201...200mm-f2-8-is/
This seems to be one HECK of a lens...