CHECKING TO SEE IF THE WORLD IS THE PROBLEM:
Sometimes, your world itself is the cause of lags and crashes, mostly chunk error related. To test and see if your world is a problem, you can do the following:
· Login to the panel
· In the World box, type in a new name (such as test)
· Click save
· Restart the server
· This will create a new world folder in your server's directory called "test" (or whatever you named it) and will be a clean world.
· Check your servers console to see if the same errors are on there. (If you have multiverse plugin, make sure and disable it first).
· Join your server and run around
If the servers lag is gone, then it most likely means that your world has a problem. This can be caused by:
· Too much TNT
· Overspawning of mobs
· Water/lava falling from high
· Redstone pistons
These have to be removed from your world if you want to be able to use your original world.
To change the world back to your old one, simply change the world name back to what it was in the world box, click save and restart the server (capitalization and spaces matter, make sure it is exactly the same name as before).