[danmdan]

Since this is new, take it up with the supplier. Ed.

Neither lens or camera body are new.

What is obviously happening is that as soon as the lens (during a panned video shot) sees another object at a different distance to that at which it initially focussed, it deliberately goes out of focus so as to ascertain sharp focus on the new object/scene - presumably by some sort of contrast detection..
This happens very quickly but leaves an obvious out/in focus jump on the resulting film.

It works perfectly with stills, refocusing just before each shot as the shutter release is slowly pressed. If this is a characteristic of all (motorised) focusing lenses then it is not nearly as good as my iPhone at holding focus during a panned shot.