try the camera in Aperture priority with an f stop under f8 i.e. f8 or f5.6
I discovered that when I have the camera in auto ISO and Autoexposure in bright light my camera is unusable for video but works fine with stills tho.
I now set the iso manually and do aperture priority and have no problems. At high apertures in video something is wrong in the exposure options and the lens is so stopped down it hunts for focus. I can duplicate this on every lens I own