Forgive me, I don't know any specifics. All i can tell you is that A launcher update had occurred, (many do so didn't think too much of it) and I decided to try out the 17w06a (made back up of my world) I noticed some minuscule lag, chalked it up to just my world loading up. Tinkering around, and noticed when i put a command in a command block, your normal scoreboard testing for scores and such, hadn't made the objective yet. It caused EXTREME LAG haven't a clue why. Went around to a village and then all of a sudden chunk rendering failed and i could see through the mountain.. Various things kept going on and then i was walking around and BAM everything stopped the game froze and stopped responding.. Took forever for a crash report to pop up which I also thought was odd. I don't know what to call this one. It says something about memory..