Getting error when saving OVRSpatialAnchor to local

Found this post because I ran into the same errors this morning. You probably resolved it after a week but I'll just mention that you can get this error if you try to save the new OVRSpatialAnchor object immediately after creating it. The creation process is asynchronous - it's mentioned in the docs that the uuid is not immediately valid - but they don't seem to describe any callback process. 

My use case is the user positions a grabbable object in the scene and then saves that position as a new anchor. So, what I'm doing now is after instantiating a new object with the OVRSpatialAnchor, call a coroutine that waits for newAnchor.Localized == true before attempting the save.  I might try looking again to see if there's a way to get a newly created instance to trigger a callback.