Game going in slow-motion then accelerates

Only in endgame areas (hideout, some maps, endgame town), the game will periodically slow down (no stuttering or lag per se, everything is in slow motion), and then accelerate (I’m talking rocket boots moment) to catch up with the lost time.

This has only started recently. Game was fine for my first 100 hours of play.

Switching graphic settings and going back and forth between Vulkan and DX12 doest not solve the problem.

Help

I have experience this as well, but I'm often only getting 20 fps recently.