Windows scalling issue Win32 App

I’m making Windows game. The base resolution is 1088x864. Maps are created in Tiled and draw in Solar 2D with Ponytiled module. Resolution is 32x32 per tile. When I’m scalling window by dragging sides on build app these artifacts appears. In config.lua I set “letterbox” scalling.

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Is there a way to config to make upscalling more even?