I have a skeleton grinder from a spawner, and I was working near it, so skeletons kept spawning. My game then crashed when I went to where the skeletons were collecting for me to kill. Now the game crashes every time I try to load the world, wish is irritating as I have made a lot of progress. The same thing happened when I bred my herd of cows, but at least I was able to get onto the game to kill a couple of cows before each crash until it stopped crashing. It seems that it can’t handle many entities in a small space.