This entity is represented by a member property whose underlying field is the same as the underlying field for some level in the model. If a level and a property have the same underlying field, only the level can represent an entity.
In an OLAP or mixed SQL/OLAP model, every OLAP object has an underlying SQL object. You cannot have one entity representing the OLAP member property and another entity representing the OLAP level if the member property and the level have the same underlying database fields. Only one entity representing the level should exist.
To correct this error:
Compile-Time Error Messages (Authoring Object Model)
Expanding an English Query Model
How to manually map OLAP objects to the underlying SQL database objects