Do someone is accessing your sdm application replicated instance? as this need to be set to offline reporting mode to avoid users been eventually be able to create ticket there.
except of the above or if you change data manually in the database the option above will not have impact.
Do the ID of the record are the same or only the ref_num?
You must start from an empty database on the subscriber and apply the initial snapshot.
if this is done replication index will prevent to have duplicate record
How did you get the mdd on your replicated server?