When merging two constituents, a user may receive Error: Data could not be saved. The DELETE statement conflicted with the REFERENCE constraint "FK_FINANCIALTRANSACTIONLINEITEMADJUSTMENT_CONSTITUENTID". The conflict occurred in database "SMP_EC_30", table "dbo.FINANCIALTRANSACTIONLINEITEMADJUSTMENT", column 'CONSTITUENTID'.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.
Workaround: Instead of marking to delete the Source constituents, choose to mark it as Inactive.