..................... when you go to remove the Day disc snap ring/circlip. And some Neanderthal has put it on the wrong way FFS! Even though it tells you how it should be fitted on the day disk right under your eyes! And it's explained in detail in many of Seiko's Tech Guides. So what should have been an easy lift off with a hand remover, turned into a search for a pair of suitably sized screwdrivers, one to spread the gap, and the other smaller 0.6mm ø screwdriver to lift the snap high enough to get the correct tool beneath it. End rant.
I take it this is like the watchmaking equivalent of putting a VHS tape back in the case without rewinding it or stripping the threads on ikea furniture