Here's a Video of the problem: https://drive.google.com/file/d/0B6gu9bohJW1HR21ueFhmakRTdVk

I can't place doors on some blocks, while on others I can. It's random on which blocks I can place doors...

What happened:

"All players on our Realm are unable to place doors where they once were.
We opened doors and they would disappear not allowing us to replace them. The issue is still on going today.
However, on single player world the issue is non existent, so far only on the realm." -Jonathan Long