Well, cheddar tends naturally towards crumbly, because the curd is low pH and low in Calcium. The differences in texture may be from improper pressing - if the cheese was pressed too hard, too quickly, the outside rind quickly closes, and this seals in the interior whey, not allowing it to escape as it should. Then the inside would continue to (over)acidify. The irregular holes and lower-than-desired curd adhesion inside also testifies to this (the holes come either from air or whey pockets that were not pushed out during pressing). Those are my guesses.