Can you find the exact point where this happens? More properly: is there
- a point when it happens or
- is there hysteresis?
1: if you find this point, small back and forth movement of the focus ring makes big repeated jumps (do not play with this too much though ;-) )
2: you focus in one direction, then it jumps, but you have to go backward with focus considerably before it jumps back.
Because:
means that the lens element path is somehow weakened or broken or has some play or dirt or some kind of a friction (there are several types of greases being used in a lens to properly achieve the required friction);
usually means that a lens element has some play inside the lens holder ring - God knows its proper English name... It is two rings glued together on each side of the lens element, holding the lens element usually steady. So when the lens element is loose, and the lens is breathing, it can also do a pop like this, although not this distinct.
Also, does the same error happen if you look directly vertically down? (Do not look vertically up, as small debris can drop into the camera from a broken lens during focusing...).
From the video, you can hear a "knock" just when the change happens, so my guess is point 1. Instead of sliding properly, there is a break when moving from one path from another, like those internal paths are not properly aligned, and that makes the sound and the change in optical axis. My bet is that this happens one direction pretty rapidly (so: knock), and not the other way (no knock...).
It seems that this is a construction error, so your best bet is to have it fixed or replaced.
