This behavior caused me to waste almost an entire day. In our case, we had a group of animations in a single controller that set active/inactive on some UI elements. When we would get to an animation state that didn't include a prior UI element, it would get set to the UI Element's last active value, even though it wasn't in the track list. We noticed that this was happening when we tried to toggle active/inactive in the inspector but something was locking the value. Turns out it was Animator. The expected behavior here is that only the tracks that are in the active animation should be affected. Our solution is to manage active state in code and remove all tracks relating to Active from the entire animation controller.