Well, I resume the history.
I was playing in a normal 1.11.2 world, completely vanilla.
Then I decided to install forge, with Lunatrius core and Schematica mod to build a great big thing.
Then, when I built It and I wanted to go back to the vanilla 1.11.2 and I enter the world, all the observers are broken. They are stuck in the *Gives signal* Mode. You have to break them or move them with a piston in order for them to update.
I tested if updating to mc vanilla 1.12 it would update, but nothing. I tried with only forge, without any mods, and definitely it's Forge's fault, cause without any mods, the issue keeps happening.
Its important that it only happens when you try to go back from the Forge version, to the Vanilla minecraft.
I even tried to place new observers in the vanilla, after going back from the forge. And surprise, went out of the world, entered again, and there was no trouble with those new observers, only with the old ones, that were placed with the forge version running.
I checked in the internet, but theres 0 information about this, so I hope here we find something.
*Edit* The forge version is: 1.11.2-13.20.1.2454