We have activated the standard duplicate rules and matching rules for Account. Generally, they seem to work and the duplicate records get written into the tables DuplicateRecordSet and DuplicateRecordItem. There are a few exceptions though that do not get written into the databases. When the duplicate Accounts are inserted manually, they are detected as duplicates, and the duplicate Account message appears on the top of the user interface. But this query does not give me any results for the specific duplicates, matching by name:
SELECT DuplicateRecordSetId, Id, IsDeleted, Name, RecordId, Record.Name, DuplicateRecordSet.Name, DuplicateRecordSet.RecordCount FROM DuplicateRecordItem WHERE IsDeleted = false AND DuplicateRecordSet.RecordCount > 1 AND Record.Name = 'Test Account'
For an example, the duplicate matches via First Name and Last Name and Billing Address so that the Account Matching Rules should get triggered. When I try to reproduce the error, the records get inserted into the duplicate tables just fine.