[2022] Steady FPS drop even in menus or when paused, disappears with yesmen.

Is that save started under 1.6.1.2 or the current patch?

If the former, please revert to that game version in the Steam betas tab for this game. If the latter, please post that save in Bug Reports here, thanks!  

Thanks for that great work! Did you report this in Bug Reports, as I suggested?