I think it's definitely a lot to do with the lens being used. The 14-140mm was always designed for video so has lovely AF. I have always found the 20mm to be truly awful for video AF. It hunts all over the place and is just not any good. As always, for photo it's fantastic but video, not so much - though a lovely lens video quality wise. It will be interesting to see how all of the AF lenses stack up on the GH5 as more people play with it.