I switched the game over to another laptop and was wondering why it was running slower.
The FPS was capped at 40, which matched the refresh rate of the display. Changing my refresh rate to 60hz boosted the FPS to 60 again.
This only seems to happen when the game is in windowed mode and is not maximized.
Upping the refresh rate to 75 had the game at 60fps still (so maybe runs at 60fps max)