title: Errors in the OLAP storage engine: The attribute key was converted to an unknown member because the attribute key was not found
body: <p>I got this error when processing the cube.
  Errors in the OLAP storage engine: The attribute key was converted to an unknown member because the attribute key was not found</p>
  
  <p>But I set the Dimension and attribute Null Processing properties to Unknown Member, which means it should not fail, but consider it to be unknown. </p>
  
  <p>Why am I still getting the error?</p>