It occurs both in single player and multiplayer worlds. I have had entity crashes before, but honestly I cannot for the life of me remember how I fixed it.
I use MultiMC to keep things nice and tidy. I have tried a normal Minecraft setup, too, and it crashes.
I have tried removing all of my mods, then half, test, then the other half, test, etc., etc., all the way down, and yet I will still get crashes when I have all of these ones that add entities. Yet, just a few days ago, I was playing without quarrel. (Until I had to reinstall all of this because I got a new harddrive; therefore I know I have plugged something in wrong.)
Google searches I have been trying: "Solved Minecraft entity crash" "Solved net.minecraft.util.ReportedException: Ticking entity", etc.
Any advice or helpful tidbits would be greatly appreciated! Thank you very much!