Matt - Thanks for hleping out.
Ben,
Matt is right, if you have Customer conflicts, this will prevent the use of the FullName field as it will no longer be unique. If there are no conflicts, you may still have duplicates. To find them, I'd export the Entity table and include the Entity Type, FullName and RecordID fields. Then, after the export, select the FullName column and use Excel's Conditional Formatting option and select Highlight Cell Rules > Duplicate Values. This will mark the duplicate values with a different color that you can then filter the sheet for and find your duplicates.
Hope this helps,
- Adam