Essentially, I have a base (empty) scene that only contains UI, and several other scenes that get loaded which contain the AR content (including the ARCamera).
When I load the first scene, it tracks no problem. As soon as I load another scene, it won't track. Keep in mind that each time I load a scene I'm creating an ARCamera, so this may be part of the problem, but I don't know. It all works fine in the Unity editor, but not on a device.
And note that whichever scene I load first, it works fine. But whenever I move to another scene, it no longer tracks.
Hope this makes some kind of sense.
I actually meant keeping the experiences in their own separate scene files and calling a regular scene load for each. Then each scene would have it's own camera and set of assets. Unity is pretty smart about clearing stuff out between scene loads and freeing up that memory. Additive scene loading requires a bit more hands-on for managing what you want to keep or discard. I just wasn't sure if its better to keep the AR Camera setup live throughout the game.
Instead of activating/deactivating those models entirely, you could just grab a reference to their individual mesh renderers and toggle those on or off.