I recently upgraded my main monitor to 4k, so today I changed the Windows text scaling to 200% to read the file open dialog box better, and the external monitor preview on the 4k main monitor is now scaling based on the TEXT Windows scaling! I know this because I can set Windows display text scaling to 100% and it is fine.

My 2nd 1080 monitor works fine.

If I turn off "scale to fit" for the external monitor, then I get a 1080 picture in the lower right of the 4k display.

Version 15 is fine.

I've tried setting to default layout, restart, switching external monitor back and forth between displays, and nothing gets it out of this mode.

There was no problem until I changed the Windows display text scaling from the default 150% to 200%. Changing it back to 150% doesn't help.

Surely there's a registry value that can be reset, but which one?

Reinstall would probably loose several dozen fx presets.

My 1080 monitor is an older one and not that great for color.

I have been thinking about upgrading it to 4k, too. When I try to move the cursor to it, it hangs unless the cursor is in the top 1/2 of the screen - I assume because Windows thinks there nothing at the bottom since it isn't as large. So then I wouldn't have any monitor that external preview works on.

All suggestions welcomed!