- field_collection_item__field_CHILDCOLLECTION_X tables exist for all child field collections EXCEPT the one without the UUID
- field_collection_item__668c612c1b table exists for the child field collection under consideration (will call it field_CHILDCOLLECTION_Y). ... It has the same structure as the other tables with valid data for field instances.
- field_collection config item 'field_CHILDCOLLECTION_Y' has null uuid value.
- DELETE field_CHILDCOLLECTION_X1: OK.
- DELETE field_CHILDCOLLECTION_X2: OK.