SQL Bug - MDS allowing duplicate Codes in entity

We have an issue with MDS SQL 2012 CU5 allowing duplicate codes in an entity.

NameCode
9420045064620100902001XXXL
9420045064637100902001XXXL

This is occurring in our production MDS solution on a Barcode entity.

The duplicates can be removed however they appear to be linked in some way so both must be deleted - this is a temp solution as duplicates then re-occur randomly. 

We have tens of thousands of entries in our Barcode entity and these get ETLd to NAV and AX, there are only 14 duplicated entries but the flow through problems areenormous.

Thanks,

Chris McKoy