Whenever I enter a cell with a certain activator placed in, it disappears. I actually can see it slowly fading away, but it never comes back. It's got no scripts attached to it, is not set to be initially disabled, and is in an interior. What other reasons could have caused this?

Got it sort of working again. The mesh will fade out, but fade back in a few seconds later and stay.
And this is only with a script attached now.