I crash at random intervals in a pre-existing world (made in 1.9) when I am near my sheep pens. I only crash near the sheep pens, and in total there are ~80 sheep, of a variety of colors. The crash report is attached. This crash has occurred multiple times in a short amount of time. This did not happen in 1.10.0. I did go to the coordinates in the crash log, and there is indeed a sticky piston there. Looking at the position of the piston relative to the sheep pen, it looks like the crash occurs when I head back towards the area with the piston, causing the chunk to load. The crash does not occur every time though.