Question:

Why does the rule job CSV output file states: Failed To Delete and the Reason for Failure is NON_BLANK in Vault CDMS? 

Answer:

This is a warning message. Failed to Delete appears while attempting to delete non-blank forms. The message does not indicate an error but lets clients know that the form instance is not automatically deleted by the rule until the form itself is reset to blank.
  
The form only deletes if all of the following conditions are true: 

• The form's instance status is Blank
• The form is not locked or frozen
• None of the form's items are locked or frozen

Related Documentation:

Vault CDMS Documentation: Running Rules