Randomly limited to 30FPS. Frame rate drops

Well a bug has been bothering me sometime, where the frame rate seemingly drops but theres no indication as to why... For example the frame rate is running at 60fps, then without moving or anything being different it is suddenly running at 30FPS... Then after a few minutes back to 60fps...

While i had fraps on i could see the frame rate, and the game was going to 30FPS even though it was being reported as 60fps by fraps, this isn't a fraps issue however because it accurately reports frame drops in congested areas...

So yeah, theres some bug with how the game handles frame rate. No idea why though ofc.

Happens on any graphics card it seems (just upgraded recently) and multiple others have reported this happens too.

Specs:
I7 3770K 4.2GHZ
GEFORCE GTX 780
8GB DDR3 1600
128GB SAMSUNG 840 PRO SSD