I tamed two wolves, and bred them, so i have one baby wolf and two adults. In an effort to travel home, I found my nether portal that had a shortcut to my home, and I entered it. The wolves came in as well, but they seem to be stuck in the nether. It takes a little time before they can be pushed into other portals, and after I pushed them to the overworld, they pretty much come out of every portal that I go through, and might have been causing crashes. There are three portals in the nether, which I pushed them in/accidentally brought them through, and each portal has its own three wolves that come out in the overworld, while there is just one group of three in the nether. I tried killing them, and trying to do so crashes the game after they die.
This is in survival, a three day old world, sized 142.8mb that has less than 10 players that did stuff in the world.
A crash might roll back changes done, although I have no idea if the wolves are also involved.