I've had my Mi Box 3 for a few years now. I have a Seiki 42 4k tv that will do 4k at 60hz and it has HDMI 2.0 ports, but I can only get the Mi Box to work at 4k30hz. I believe the tv is only 4:2:2.
At first I thought it was because of an older HDMI cable. I bought some 18gbps HDMI cables but when I switch to 4k60hz in the display settings, the screen flashes green and static in an alternating pattern.
I've powered off the box, tried plugging in the cable a few times, but it will only display at 4k30hz.
Any ideas?
Maybe you need to enable high bandwidth mode on the TV? For Sony TV's you have to do this for example, don't know about yours.