Whenever I get on one of the snapshots that is 15w31a and up, it acts as if it has a very small FPS count. It does not lag on the menu, but in the game itself. It also seems that keypresses do not work, even when I hold down say, the spacebar.

I have tried changing the video settings to fit my computer more. And I have tried turning down the master volume to 0% in case it was a sound problem. Neither of these worked. I have tried creating new worlds in the case that my old ones were in some way corrupted, but it does not help.

Note : This isn't just a small drop in FPS, this makes minecraft unusable and I have to pkill it.