Why do I see an error about reparenting when I dedupe?

If you see the error: "When reparenting [object] records: could not save non-master child record : duplicate value found: [field] duplicates value on record with id: [Salesforce ID]" here are some things to check:

Sometimes Apsona has to clone child records during the reparenting process (see this article for more details). There is a known issue where a dedupe action fails to reparent child records if the object has a field which requires a unique value, as compared to all other records in the system. The field would be marked as such in Setup:

The current workaround for this issue is to temporarily uncheck the ‘unique’ checkbox for the field that is causing the failure so that the dedupe does not fail.