Put the summary of the bug you're having here

What I expected to happen was...:
A normal working spawner

Describe what you thought should happen here
The Skeletons should just spawn a walk around, and stop spawning after like 4 spawned

What actually happened was...:
There were more than 50 skeletons not moving in a room , causing huge fps drops.

Steps to Reproduce:
1.Find a spawner room.
2. ...
3. ...