Iron Golems keep spawning in/on unspawnable places in my realm.

What I expected to happen was...:
I built an area for IG to spawn in one specific area.

What actually happened was...:

IGs keep spawning in areas they shouldn't (on glass, in walls, etc). They are also spawning outside the width/depth that they are supposed to be.

Steps to Reproduce:
1. I built an area and an iron farm above it
2. ...I had to move it to the sky to keep the IGs from spawning around my camp where they aren't supposed to.
3. ...Half the time when they spawn now they aren't spawning in the kill chamber, they spawn in weird places.