Assigning User Defined Value to UDO

I have created a UDO based on Master Data and Master Data Rows. When I try to assign a query to one of the UDFs in the UDO via the User Defined Value I get the following error, "Exclusive code already exists, 'xx'"

The xx is because depending on when I've tried this I get a different two digit number every time. I can't seem to get it to stop erroring on any of my databases.

Any ideas?