Minecraft crashing when playing on servers. Not just one server

Put the summary of the bug you're having here
When i go on to servers like the nexus and play capture the flag, if i get killed or just at random my minecraft just crashes
What I expected to happen was...:
Describe what you thought should happen here
?- lag
What actually happened was...:
Describe what happened here
my minecraft crashed
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...go onto the nexus on a mac (thenexusmc.net)
3. ...play capture the flag and get killed
This also happens on shot bow when i play the ghost game.
Thanks and please fix