I think this is resolved if the behaviour is as David Mendenhall mentioned.
It hasn't been fixed in any of the bugfix updates.
It takes forever, but can be fixed by entering a world.
There is nothing else wrong with endermen, they just performed all of their actions 3-4 times faster. And no, it wasn't raining. I have noticed that this bug occurs mostly on flower plains.
I don't know, just play on survival on hard or normal difficulty, then find an enderman and you will see how he runs.
I thought in Minecraft PE I could make a staff of knockback by enchanting a stick with an enchanted book 😞.
It doesn't affect my current version of minecraft (0.16.1)