I recently hammered some nails into concrete block/brick walls. For those who dont know, those who live in wooden frame houses, one first uses a masonry drill bit to drill holes. Then drive a wooden peg in the hole. Then if you are diligent, screw in the screw. Or just hammer in the screw into the center of the wooden peg.
Having given that background, without thinking I hammered in some nails (screws, to hand pictures) wearing my favorite IWC Portuguese annual calendar from ZF on the hammering hand. It is such a beautiful, functional watch. The next day, or tow, I notice that the date change has suddenly misaligned by 6 hours. Which I had spent pains to fix some month or two ago! The only explanation I can cough up is the impact forces transferred from that hammering affected the movement. Other that that, this watch was within +/-3s over a period of 2 weeks.
So, in summary, impact forces do affect a mechanical watch. More so, a rep. Somebody said he dropped his watch & it functioned fine after a drop on tile from 6". I offer that a drop from 36-40" on tile dislodged many components of my ZF Calatrava. I suddenly get the urge to test this procedure on the YM I am wearing now, but I chicken out.