Bukkit Kicks Players Every 5 Minutes!

Help! I can't seem to fix this problem... Its not my computer or server, it has 1380 x 1380 memory and i know that it is something to do with bukkit/spigot (im using spigot), cause i make vanilla server and runs fine, but bukkit/spigot, it kicks players every few mins, and its not a plugin or world cause i created a new bukkit/spigot server with no plugins or multiple worlds and still kicked people, and also maybe here are the reasons it MIGHT be kicking people:

1. I got rid of the End World and also disabled it in Bukkit.yml.
1. I got rid of the Nether World and also disabled it in the server properties file.

Maybe you can help me please? Please please help me!!!

Btw they get disconnect.genericreason and sometimes disconnect.EndOfStream
And it says this when they are disconnected :

Internal Exception java blah blah blah...

 

Locked. We are only able to support CraftBukkit. You should seek support for Spigot from their forums.