This is probably one of the most in-depth lens teardowns I’ve seen from Lensrentals. Their efforts weren’t by choice, though. The lens lied to them. The team recently posted a teardown of the Canon RF 100-500mm f/4.5-7.1L IS USM lens that had a broken element inside it. It appeared as though the element might reside inside the stabilization system, which is relatively easy to remove.
It turned out, though, that the IS system of the lens was simply masking the true location of the broken element. This resulted in the need to pretty much completely dismantle the entire lens, down to almost its core constituent parts, in order to track down exactly where in the optical makeup it was.