If that's the case, I don't know how to find the problem and fix it. Try turning on 'Show FPS when in fullscreen' (or whatever it's called) and playing in fullscreen. After that, meddle with settings to see if anyhing helps, which it probably won't.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
