I summoned two animals with minecarts on top of them.
I made one animal move towards the other with the /tp command.
Once it bumped into the other animal, the game bugged out.

Steps to reproduce:
1. Create a superflat world.
2. Do

/summon Pig ~5 ~ ~ {NoAI:1,Rotation:[0:90f,1:0f],Passengers:[{id:"MinecartRideable"}]}

3. Do

/summon Cow ~-5 ~ ~ {NoAI:1,Rotation:[0:90f,1:0f],Passengers:[{id:"MinecartRideable"}]}

4. Put this in a command block(Repeat/Unconditional/Always Active) :

/tp @e[type=Pig] ~-0.2 ~ ~

5. When the animals collide, the game becomes buggy (can't run commands, can't exit world, etc.)