Hi, I was messing around with my Ninja V and my Sony a6400, and I notice that when I put the HDMI on 1080P output in the HDMI Menu, and the camera is set for 4K 25P Recording, I can record HD 1080 25p on the Ninja V and with much better resolution. Anyone that has this configuration, please try it out.
You need to select on the menu 4K output select: Memory card+HDMI.
You loose face tracking but I always use manual focus.