This issue occurs when an organization constituent has multiple relationships with individuals that are marked as primary contacts.  Each organization should be limited to one relationship that's marked as a primary contact, but this may occur if this constraint is turned off when records are converted.

1.  Go to the organization constituent record and go to the Relationships tab.
2.  Locate the individual relationship record that should be marked as the primary contact, and click "Edit."
3.  Click the Save button to close the record.  When this relationship record is saved, all other relationships that are incorrectly marked as primary contacts will have that checkbox unmarked.