when it my world I started building a house and them build a wall around my house out of netherrack and lit it on fire then I built a well and organised some things in my house, I pressed escape and clicked quit to title. a few minutes I returned to the world to find most of the netherrack unlit and huge chunks missing as well as a lot of other blocks I had placed. when I opened the chest some items were missing, some items had duplicated and some had moved to a different chest. I haven't tested this in other worlds so not to risk messing them up the problems occurred both in singleplayer and LAN multiplayer.