Planning Block Assembly is at the same level as the B0 Block.
Normal: Should not impact you.
Block assemblies must be the children of a block. Block assemblies with this error, however, are children of the project root, as B0 is.
The cause is drag and drop errors.
This problem should have no impact on you.
What You Should Do
A database integrity repair SQL script or COM tool has been provided to correct this problem.
Open the model.
Run the Clean Database custom command.
Select the object in the list of objects.
Click Clean Now to repair the object.