This is just a common video glitch which can be seen in many other videos of objects that move relative to the camera. Hence why nobody at the time saw it and it goes away each time the shot changes.

I believe it happens because the video encoding saves space by only recording changes between frames rather than recording each frame separately. That's why only moving objects are affected. Also I believe the encoding records when a group of pixels move across the screen without substantial changes in color rather than treating each pixel separately, which would explain why the glitches move along with the object they are on.