Steps:
1. Create Cube and Sphere as child
2. Make a prefab out of it (left instance in the scene)
3. Delete prefab asset
==> Cube and Sphere is red now
4. Delete Sphere
==> Color changed of Cube is changed as it was plain GameObject
5. Drag Cube to the Project browser
==> Confirmation window appears (as it thinks it is a prefab instance)
6. Choose Original Prefab
==>
"AssetImporter is referencing an asset from the previous import. This should not happen."
"Assertion failed on expression: '!GetPersistentManager().IsStreamLoaded(metaDataPath)'"
"Asset import did not unload metadata path. This will leak memory. File a bug with repro steps please. (Assets/Cube.prefab)"