A document does not render in Vault. The message that displays in the Document Viewer states that: The attempt to merge fields for the document has failed. Re-rendering the document does not fix the issue.
There are Merge Field formula(s) in the Source Document that reference a Document Field that has the same name as an Object in the affected Vault. This only causes an issue when the Document Field is a non-reference field (i.e. any type other than Object or Lookup field).
To fix this issue, the name of the Document Field should be changed so that it does not have the same name as the Object. Once the Document Field is renamed, the Merge Field formula(s) should be reformatted to reflect this change in the Source Document. The Source document should then be re-uploaded to Vault.
Vault Merge Fields Documentation: Using Merge Fields for Microsoft Word & Excel