FPS capped to 155 when game is in focus

Since I believe the last update my in-game FPS is limited to around 150-155 when I am playing the game with my usual settings and in Full Screen mode.

Interestingly enough when I alt tab out of the game or leave focus the FPS actually increases to what I have set in-game (limit - 299) as expected.

This seems to be a bug introduced in the last update.

Expected result: 300 FPS in-game when in Full Desktop mode.

Screenshot below showing FPS surging to expected value when game is minimised or alt tabbed out: