Are you making changes to the slave by authenticating using the same dn as what is specified in updatedn? If so, then your slave slapd believes that the changes you are making are coming from the master, and therefore, doesn't refer them back to the master. (consider the alternative - an infinite loop!)
To work around this, authenticate to the master (not the slave), and create an entry that you can authenticate to. This change will propogate up to the slave, where you can then make changes, and watch them propogate to the master (and out to other slaves, if applicable).
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OpenLDAP Faq-O-Matic : 
Why don't my changes on a slave directory get referred to the specified master?