Display type option resets

Le-loubean  Do you have GeForce Experience installed, or perhaps the newer Nvidia App?  GFE at least has an option to "optimize" your games, which could be reimposing fullscreen mode.  Other gaming-related apps could do the same, although I don't know of one with this specific feature.

If the other game options you're changing are NOT graphics settings, that would explain why they stick.  So a good test would be to change another graphics setting, for example enabling or disabling post processing or uncompressed sim textures.