I have the exact same issue, both in borderless window or fullscreen. Only started happening with latest Oct update -> well, after they fixed it not working before. Funnily enough, when I set my monitor to 'Ultimate Engine" (freesyncs from 48-72fps) it actually works but causes a crash after some time. Setting it to "Standard Engine" (30-60fps), it just doesn't work at all. It used to work on both before the Oct update.
