When you play on a wifi server. When you copy the world it doesnt copy the whole thing

What I expected to happen was...:
I would have everything i built in the world

What actually happened was.....
It would only copy half if not none of my builds

Steps to Reproduce:
1. Go on a multiplayer world
2. Build stuff
3. Quit and copy map
4. Join the copied version of the map
5. Walk around the world

bug is in creative and survival
Also when you copy maps chest items disappear