multiplayer server(skyblock) game crashed a lot

Put the summary of the bug you're having here

What I expected to happen was me walking in minecraft
Describe what you thought should happen here

What actually happened was back to launcer with crashreport
Describe what happened here

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2.logg in skyblock server
3. walked around for just a bit
4.crash to launcer with crash report