Symptom
The content deployment import process cannot handle duplicate column names between site collections and sites. This will result in an error message similar to the following:
A duplicate name "MyCustomField" was found.
at Microsoft.SharePoint.SPFieldCollection.AddFieldToWeb(String strXml, Boolean checkDisplayName)
at Microsoft.SharePoint.SPFieldCollection.AddFieldAsXmlInternal(String schemaXml, Boolean addToDefaultView, SPAddFieldOptions op)
at Microsoft.SharePoint.Deployment.FieldTemplateSerializer.CreateField(SPWeb web, SerializationInfoHelper infoHelper)
at Microsoft.SharePoint.Deployment.FieldTemplateSerializer.SetObjectData(Object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector)
at Microsoft.SharePoint.Deployment.XmlFormatter.ParseObject(Type objectType, Boolean isChildObject)
at Microsoft.SharePoint.Deployment.XmlFormatter.DeserializeObject(Type objectType, Boolean isChildObject, DeploymentObject envelope)
at Microsoft.SharePoint.Deployment.XmlFormatter.Deserialize(Stream serializationStream)
at Microsoft.SharePoint.Deployment.ObjectSerializer.Deserialize(Stream serializationStream)
at Microsoft.SharePoint.Deployment.ImportObjectManager.ProcessObject(XmlReader xmlReader)
at Microsoft.SharePoint.Deployment.SPImport.DeserializeObjects()
at Microsoft.SharePoint.Deployment.SPImport.Run()
Cause
If you create a new column named "MyCustomColumn" in a subsite of a site collection, and then you create a column with the same name in the root site of the site collection, when you return to the subsite, there will now be two columns listed with the same name. Such a configuration will cause content deployment jobs to fail.
Resolution
Ensure that column names are unique. If necessary, delete the duplicate column, and then recreate it with a new name in either the subsite or the root site. When you are finished, rerun the content deployment job.