Update
Tried resetting game graphics and vorpx settings to defaults again and z-buffer modes started working. However, they only work at 1280×720 windowed, which is the resolution the game defaults to when settings are reset. Changing from this resolution seems to be breaking z-buffer modes for me. Vorpx will change to a different resolution and on restarting the game the z-buffer modes are no longer in 3d. Turning off vorpx resolution changing and changing the game resolution back to 1280×720 then restarting the game reenables the z-buffer 3d reconstruction.