>Ok, the process finished and produced 117 problematic records.

Last time I had a problem like that, at least the incoming data were created within the system - i.e. whenever a patient's data were to be written anywhere, the operator would try to find the patient in the patients table, so we'd have the SSN (well, Hungarian Unified Citizen Number) which was used as ID, and if that wasn't available, the system would issue a temporary SSN (with a bunch of zeros or nines in the first group) which was used until the proper one was found. Happened with babies a lot - they aren't issued one for a couple of days. Next time the patient appeared in the system with a proper SSN, a new record would be created, and then later merged with the temp record - more or less manually, i.e. there was a form showing all the non-blank data from both records, and the operator would choose which should be copied to the permanent record.

Another cause were illegible names and DOBs on the papers unconscious patients may have, which could cause spelling errors (although Hungarian is rather immune to those).

If your data are coming in with less than sufficient info to ID the patient... you're lucky to end up with just hundreds of mismatches.