Random freezing in world..

This happens on 0.11.1 also. It maybe related to chunk updates on large maps when a chunk hasn't been accessed for awhile and contains active blocks like fire. I've noticed that when you move out of a fire area (I do this routinely for deforestation) and then re-enter it, the fire effect rapidly catches up on the reloaded chunk. If you use fire as an ornament (ex. on Nether Rack for fireplaces or torches) this seems to cause these issues. I have entire cities with fireplaces, and the game will freeze every time I walk 16 blocks and a new set of chunks loads.