DPI scaling is the only issue I am aware of that has caused issues. I am not familiar with Win10, so if that is disabled globally, try opening another application. A VSTi would be a good choice. If it persists, I would start researching the monitor. With DPI scaling disabled (globally) do the GUIs of plugins inside of SONAR exhibit the same behavior?
Does the new monitor have the same connection as the old? Any upscaling, such as 4K upscaling may also be an issue. Drivers, etc., as well. Seeing this issue upon replacement makes the new monitor suspect.
What are the two monitors in question here?