Imagine the following scenario:
An entity is displayed on the globe that has certain availability defined.
User clicks on entity, bringing up the info box.
User clicks the camera icon to track that entity.
The timeline progresses to a time when the entity is no longer available.
User closes the info box.
As far as I can tell, there is now no way to stop tracking this entity. There is no way in the standard viewer widget to stop tracking an entity except through the info box. The info box cannot be brought up if the entity is unavailable. As a result, the user can no longer move around the map because dragging the mouse operates as if an entity is being tracked.
The only way out of this is to select another visible entity if one exists and is visible within the current map view, or to adjust the timeline to bring the entity back into availability.
I’m not sure what the best solution is. Perhaps while an entity is being tracked, there is always a widget visible that shows it being tracked (beyond the info box, which can be dismissed). This also makes it clearer that tracking is enabled, even when the entity is still visible, but the user has dismissed the info box.