Merge statement causing deferred updates

Hi-

Environment is SQL2012 Enterprise.
We have two tables that are replicated (transactional). The source tables are updated via the MERGE TSQL statement. The columns being updated are not part of any unique or primary key, yet we're seeing the updates replicated as Delete/Insert pairs. We tried setting trace-flag 8207 but this did not help. At this point it seems our only option is to abandon the MERGE statement and insert or update the old fashioned way.

Any insight/assistance is much appreciated!

Thanks