One of parameters (value: Array) is not of the type Integer - initially observed during import, but same when visiting Contact Record
Ok - so stroke of luck - was checking the Contact table and spotted that one of my problem patients had 'array' in the Preferred Communications table, as did the other record which the import failed on. As did about another dozen.

Once I changed the value in the db i could then visit the record.

Which I guess poses another question of how did they get array in as the value and I may post that as a separate question.