Play in fullscreen and change the frame rate limiter ingame to no limit. Then, fully close and reopen the game so windows focuses on it correctly, resource wise.

There has been a problem playing in borderless with 1/1 fps scale in this game for years and they wont fix it.
Happens to me every few days as well and Im using a 1000$ 2080 TI graphics card.
Not a single gpu setting will help it, its 100% this game.