I had around ten dogs on leads attached to a fencepost. All the dogs were standing, so when I moved the fencepost with a piston the leads broke and the dogs teleported to me. The weird thing was after the dogs teleported, they didn't attack anything that attacked me or that I attacked. They still followed me as I ran around, but they didn't help in any combat and I had to restart my world to get them to behave normally again.