Caporegime
If its exactly 30 fps its sitting at, Could it be some V-Sync option? I know when you have some form of V-Sync on and it can't maintain 60 fps, it will drop down to the next interval, so 30 fps. There is an adaptive (half refresh rate) available (if you do not have G-sync on) option in Nvidia control panel that does exactly that and one for AMD, can't recall any in game option but can't check for sure.
Nah average fluctuates between 34 and 37. Good thought though.