MissingReferenceException on legacy animation SOMETIMES -- 5.1.2p2 (bug?)

We have an legacy animation that is linked in the inspector (Serialized private Animation field).
An event fires a function that triggers the animation to play.

Most of the time this works. Sometimes we get this
MissingReferenceException: The object of type 'Animation' has been destroyed but you are still trying to access it.

The object is loaded with the scene and never destroyed. The animation or the object it's attached to are never destroyed or turned off. The animation simply activates some child objects and changes some script values on those child objects.

Everything still exists in the editor. Is this a bug in Unity or something to do with Legacy animations? I'm not getting any useful search results if it is a known bug.

sim

 

Disregard. It was an issue with a singleton holding on to a reference to the script attached to an object, but the object was destroyed during scene load.