Wikimedia Bugzilla is closed!

On Monday when new code was deployed to Wikidata, the DataValue (and api) was changed to disallow null data in the globecoordinate value's precision field. 

This caused a problem when editing an item, and claims (including unrelated claims) on the item got resaved.  Many globecoordinate claims in the database have null precision. Then the system regarded these globecoordinate values as "bad", invalid, undeserializable.  

To further complicate the problem, these "bad" values were actually being stored in the database with datavalue type = "bad", losing knowledge that these had been "globecoordinate".

We updated the software to allow null precision again, for now.  Saving globecoordinate with null is okay now, although deprecated and discouraged.

It was possible for my bot to go through affected items and set the datavalue type back to "globecoordinate" to allow them to be valid again.  This fixed any "broken" items.