Hi, I've had an EF 100-400mm Mk II since March 2015 and so far it has performed flawlessly and still does in AF mode. However, yesterday I noticed that the manual focus adjustment seems to have excessive slip. I was trying to get a rough focus on a light aircraft at high altitude and with a recently acquired 1.4x Mkiii attached, was restricted to the central focus point only. The target was too blurred for me to put the central focus point on it with confidence, so I tried to use manual focus to help things along. The ring itself moves freely but the focusing is very vague and looking the distance scale movement, it seems reluctant to move reliably when the ring is turned. I don't use manual focus often, so I've not been aware of this fault/feature before. Has anyone else had this problem?