Hi, Anyone having trouble transfering elements with media items on Courier?

I am using Courier 3.1.6 on Umbraco 7.7.7

Courier works fine when I transfer items that don't use media items, however, when I try to transfer an element that references some media I get the following error:

ERROR Umbraco.Courier.Core.BackgroundTaskRunner - [Thread 5] An error occurred consuming task System.Web.Services.Protocols.SoapException: System.Web.Services.Protocols.SoapException: Server was unable to process request. ---> System.ApplicationException: Error extracting item, ID: 16bc0049-e8f5-d321-6c76-3dfbb1367a2dd8e6ad84-e73a-11df-9492-0800200c9a66, Name: Image, Type: Umbraco.Courier.ItemProviders.DocumentType ---> NHibernate.Exceptions.GenericADOException: could not insert: [Umbraco.Courier.Persistence.V6.NHibernate.EntityClasses.CmsPropertyTypeGroup][SQL: INSERT INTO cmsPropertyTypeGroup (contenttypeNodeId, sortorder, text, uniqueID) VALUES (?, ?, ?, ?); select SCOPEIDENTITY()] ---> System.Data.SqlClient.SqlException: Cannot insert duplicate key row in object 'dbo.cmsPropertyTypeGroup' with unique index 'IX_cmsPropertyTypeGroupUniqueID'. The duplicate key value is (79ed4d07-254a-42cf-8fa9-ebe1c116a596). The statement has been terminated.

It seems the system is trying to insert a duplicate but I haven't found a work around for this issue. Any ideas?

Thanks in advance.