I am using an i7-3770k over clocked to 4.4ghz, gtx1080, 16gb ram, with a 2560x1440p 144hz gsync monitor and the game just runs at a locked 24fps, if I alt tab out and go back in, it will run okay for a few seconds or until I look at something and then it will go back to 24fps. I tried playing the game in ultra low motion blur mode and locking the fps to 120fps but the ingame vsync causes mouse lag and then the fps drops to 60fps or lower after a while anyway. Is there any solution to this?

*I think I figured it out, I just reset the setting in nvidia control panel and then put them back how I wanted them and it seems to work okay now. But also Vsync doesn't work when forced on in the control panel, but it doesn't really seem to affect anything so whatever.*

Same problem here. i7-7700k, gtx 1080, 16gb ram, 1080p gsync monitor. Rebooting or alt tabbing sometimes work for a time to reset it back to 144 fps. After a few moments it's stuck at 24 fps again. Fastest way to trigger it is to cook at the oven and close the menu.

Have you tried turning off dynamic resolution?