Resolution settings not sticking

Kodi 17.3, Windows 10, nVidia GTX660ti with 3 GB, three 1920×1080 monitors set up to span all three displays for an effective resolution of 5760×1080.

1) Go into Settings/System
2) Choose Display mode for Fullscreen #1
3) Set resolution for 1920×1080.

So far so good. The display uses only the middle monitor which is what I want.

I hit Alt-Enter to switch into Windowed mode. This works fine.
I hit Alt-Enter again to switch back to full screen mode. This then goes back to using 5760×1080. It basically dumps the settings I made previously and goes back to default.

I have tried turning on Use fullscreen window and Blank other displays but these don’t get saved either.

Is this a bug? Is this working as designed? Is there a way to get the full screen settings to be stick after hitting Alt-Enter to switch between modes?