A duplicate field name ‘X’ was found.
When adding a custom Content Type that contains a metadata field to SPList/Library, you can get the error message: A duplicate field name ‘X’ was found. ( X can be the Name or ID (GUID) of metadata field). Our custom Content Type is provided via a feature. The problem comes from the order of Metadata fields in Content Type, the Note field should be after the Metadata field. <FieldRef ID="{F88D530B-705F-488A-9069-FAF5C79B61F7}" Name="RegionalOffice"/> <FieldRef ID="{9EDAB26E-CC44-4027-AB05-CB44EA3A6F72}" Name="RegionalOfficeTaxHTField0"/> If the .order of Note field is above the Metadata field like below, you can get the error. <FieldRef ID="{9EDAB26E-CC44-4027-AB05-CB44EA3A6F72}" Name="RegionalOfficeTaxHTField0"/> <FieldRef ID="{F88D530B-705F-488A-9069-FAF5C79B61F7}" Name="RegionalOffice"/>