Think something was updated because now I get screen on my smart phone as well as the A6400 screen, until I hit record.  Then I keep video on the smart phone and get the settings on a black screen on the camera.  

Hello there, thank you for reaching out. Can we double check that you were using the multi cable to connect the Sony A6400 with the gimbal? Currently we have noticed this issue and are finding solutions with Sony. We still recommend you to use the Multi cable that enables you to get the signal from the HDMI.

Thanks