Window goes entirely white when doing 'fs :0'

[VDZ]

When I start up the game, I do :fs 1 to get to fullscreen. This works. Once I'm in the game, if I do :fs 0, the resulting window is entirely white (other than the title bar) and I can't seem to :fs 1 again so it probably goes beyond a mere rendering issue.

[loftar]

Yeah, I know; fullscreen mode has always been buggy, and I've never been able to pin down what actually happens. It seems to work on some computers but not on others.

[VDZ]

It's worth noting that fullscreen (and fullscreen to windowed and back and again and again etc) always worked in old Haven on the same setup. Fullscreen currently works fine, too; I just can't switch back to windowed. I can even alt-tab without any issues.