SAP Message CC301 - Revision levels cannot be exploded down

Diagnosis
You want to create an object management record for this change master,and use the Find object function to select an object.
You see one or more revision level for the selected object, due to theexplosion of the structure overview. You try to explode a revision levelfurther by double-clicking on it. This is not possible.

Procedure
You can only explode objects down further if the special character + shows that this is possible.