[lexiconman]

To (possibly) help troubleshoot, the issue seems to be that DSPlayer isn't engaging Fullscreen Exclusive mode for 3D content. Here are the interactions between screen resolutions:

Desktop/Kodi Resolution: 2160p
2D 1080p content - Desktop res stays 2160p, engages FSE D3D11, scales content to 2160p. Looks great.
3D - Desktop res auto switches to 1080p FP, plays D3D11 windowed mode, regardless of setting configuration, scales content to 2160, filling the 1080p screen with just the top left of the movie.

Desktop/Kodi Resolution: 1080p
2D 1080p content - Desktop switches to 2160p, D3D11 windowed mode, movie stays (i.e., doesn't scale) 1080p, and only fills up the top left portion of the screen. Looks like a picture in picture.
3D - Desktop stays 1080p (but activates 3d settings), movie plays in D3D11 windowed, movie isn't scaled so would look fine, but usually causes Kodi to crash after a little while.

I'm on Windows 8.1, GTX 1070 (having downgraded from Windows 10 on Madshi's recommendation).