This is often the result when two records are merged in RE while there is a disconnect between Luminate Online and your RE server. In these situations you can find both records in Luminate Online and move all donations to the Luminate Online record who's member ID matches the system record ID of the record that remains in your RE database. Documentation on how to move donations from one record to another in Luminate Online can be found here. After all donations have been moved, the record with no donations can be manually removed in Luminate Online.