Couldn't jump on a anvil if I directly stand in fornt of the anvil.(Only in Multiplayer)

Put the summary of the bug you're having here

What I expected to happen was...:
That I could jump on a Anvil if I standt in fornt of the anvil

What actually happened was...:
I couldn't jump on it if I stand in fornt of it

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ... I don't know what to do
3. ...