The most common cause is when a user relate field has been updated via an import using the user's name instead of their user ID. For a relate field to display correctly, it needs to be populated with the user's ID. For example, if Joe Bloggs' user ID is 12345 and you import the text 'Joe Bloggs' instead of '12345', the field will appear blank in view mode. To fix this, reimport the record with the correct user ID, or manually select the user on the affected record.
