When playing HEVC videos in KODI or PotPlayer using H/W DXVA some distortion or artifact is viewed. These squares are arranged diagonally like a set of stairs or mosaic effect.
Intel’s contrast enhancement feature may be the culprit, you can disable this in the drivers control panel. Disable contrast enhancement in the video settings works fine for now.
Intel Graphics Settings > Video > Image Enhancement > Contrast Enhancement = Disable