The game runs fine when I first start, but if I open the in-game menu (viewing the map, inventory, etc.) the framerate drops in half or more, usually in the 15-20fps range. If I restart the game, it runs normally, but only until I open the menu again. Tried running in fullscreen, windowed-borderless, and windowed. Graphics driver is up to date, so is Windows.
RTX 2060, I7-7700K, 16gb RAM, Windows 10