Curious to see if anyone else is having these problems.
In manual focus when zooming out using either the rocker zoom on the grip or the one on the top handle, especially in a short burst, the 18-105 loses focus to varying degrees. If you zoom back in, even a little, it regains focus. This problem is not evident using the zoom ring or the W-T slide switch on the side of the lens. You can see this clearly if you zoom to the long end of the lens at f4 then zoom out in short bursts. Use the focus magnifier.
Cannot fine tune focus manually, it jumps from nearly in focus to way out of focus when you turn the ring slightly. This makes it impossible to follow say an interviewee who leans forward and back. You can work around this by using auto focus with face recognition if and only if the face is prominent in the shot say, as in an interview.
Otherwise, auto focus is terrible, slow and inaccurate despite the praise it gets online. The face recognition only recognizes prominent faces and often fails on persons wearing glasses.