Yeah I have this issue as well with borderless window mode since the DT patch. I'm using Riva Tuner Statistics Server to cap the frame rate since the in-game fps limiter is pretty broken. Full screen mode is fine but even switching to full screen then back to borderless doesn't fix it. Also toggling the UI completely off makes the issue even worse for some reason lol. Seems like some conflict with borderless mode and VRR.