[mclingo]

try (in KODI DS) "use full screen window" - ticked.

Also check your MADVR display modes match up, remove any 1080p modes in there, you wont need them if you are upscaling using MADVR which will be batter than your TV.

3D automatically drops to 1080p so you dont need that in there, I know only have 2160p23 in my display modes as I dont any other content.