Between beta 4 and beta 5 there was a regression with full-screen D3D9 lagless vsync on my system (Windows 10 1709, AMD graphics). D3D11 is still fine.
I have uploaded some videos to illustrate. Poor quality taken with my phone, but hopefully good enough to show the problem. Using beta 10, though beta 5 looks more or less the same.
Code:
D3D9, 4 slices: http://www.media!fire.com/file/xlzwy50woww75fw/VID_20180516_151459.mp4
D3D11,4 slices: http://www.media!fire.com/file/yit1l5fwdt4l96g/VID_20180516_151600.mp4
D3D9, 2 slices: http://www.media!fire.com/file/938prs7907k9f2b/VID_20180516_151652.mp4
D3D11,2 slices: http://www.media!fire.com/file/fu9r543dxj5ue85/VID_20180516_151734.mp4