The user receives a 'duplicate field selected' error when performing a mass update on an object part of a managed package.

Why do I get a 'duplicate field selected' error when I try to mass update a matter?

The field API names cannot be duplicated because Salesforce doesn't include the field namespace (shown in red below) when evaluating dynamic query logic.

advpm__Field_Name__c

To prevent this error, the custom field name (the one you created) has to be renamed.  The links below have more information regarding this issue.

• Sf Knowledge Article: Salesforce CPQ Quote Line Editor error 'Duplicate field selected: [field name]'
• Sf Idea: Support Dynamic SOQL "No Shadowing" Option
• Sf Known Issue: If shadowing occurs, Schema.SObjectType.<entity-name>.fields.getMap() only returns the local custom field