2017. year UHD Ambilight TV third time went to service for repair

and i had to connect Dell 2007WFPb with native resolution 1680x1050

in few resolutions picture is microscopic rectangle on the top left corner

1366x768 - NOK

1024x768 - OK

800x600 - NOK

640x480 - OK

p.s.

screenshot (all) in web-if gives full size picture