Thanks for the feedback surprisingly I do not seem to have any focussing issues at all but I'll have a look at the mounting plate to see if the movement is there, as I said earlier the 'wobble' is so minute we are talking about the thickness of a piece of masking tape
I shoot with this lens for thousands of shots of my grandsons sporting events. I am using an X-T2 and have had the combo for probably 4-5 years, I have no play between the camera and lens. I use a mono-pod for nearly all shots, and Idonotice some rotational movement between the two, there is no horizontal movement of play between the lens and camera. If you are not having the issue with other lens', then the lens mount plate out be loose. As mentioned before, you need to get this looked at in order to get in-focus results.
ARFURCROWN got a reaction from ajurjans in 100-400 Lens slight play between body and lens?