I have a similar issue.
EVERYTHING runs too fast, but when I'm in the options menu it's fine, and when an enemy gets shot, it's running at a normal speed too, weirdly.
I have a 60 HZ monitor.
Viewing post in Game plays quicker than it should
With some proper statistics, I noticed that the settings menu is forced to run at 60 FPS, but the rest isn't.
The main game runs at >100 FPS for me, and it seems like the game isn't controlled by time, which means the more FPS, the faster the game.
The developers should set a FPS limitation to 60, which isn't hard to do.