Large amounts of lag in world and is spreading.

A world in Minecraft PE that has mass amounts of lag and is currently spreading throughout the world. Me and my friend have searched throughout the world looking for spawners and anything that would create lag. But couldn’t find anything. Even made a copy of the world and went through it searching for the lag source. Even on the copy there was mass amounts of lag. We can’t figure out why this is occurring and could use some assistance.