OK - thats interesting. An issue that often arises would be where a number of people with same name ( e.g. John Flynn, his son John Flynn and his grandson John Flynn) all live at the same address but older JF owns house and grandson owes money. You can see how easy that would be to make a mistake. It is up to the party swearing the affidavit to confirm that the person is one and the same person etc.,etc. Your first line of action should be a polite letter calling on them/their solicitor to immediately take steps to deal with the issue, remove the Mortgage and reserving all of your rigts and entitlements to take such steps as are appropriate. If they won't you may need to take it further.
mf