There have been reports of this going around some said it was HumanNPC causing it are you using that plugin?

No. I don't use any NPC plugin.

Merged post

Well, except BotSpawn and ZombieHorde. You can see my whole plugin list in the beginning of the thread.

I Would try and remove any plugins that use sientists or bots see if that helps other then that im out of ideas..

Atm I am trying to check stuff this on a test server. While copying the plugins I noticed some old files
that belong to plugins I don't use anymore.
So I made clear to not copy these and clean the whole server file structure.
I I am lucky this will help.
If not I would have to check single plugins which is very time consuming cause the problem didn't appear all the time.
So I would have to wait and check over and over again.

Merged post

Ok. The NPC's are stuck again. Will completely wipe the test server now and put plugins on it at 3 stages with 30 plugins each to see what happens.
Took 6 hours today from the restart at 6am til the problem occured. Love waiting for this! :D