When not in full screen, receiving often random FPS drops/lag

For the last several months playing on multiple versions of Minecraft, when I am not in full screen mode I get massive lag spikes and FPS drops, mainly when just viewing with the camera, it occurs almost immediately on loading the world in and occurs every 2-3 seconds when attempting to play, it occurs more often and more severely when swinging the mouse around.

I've tried, 32bit and 64bit Java, different Minecraft versions, etc etc.