Are you sure its the gearbox and not the propshaft ? I’m no expert here but I heard the dual clutch and gearbox are slightly longer than the standard set up and the propshaft shorter leading to sharper angles . Check the hardy splicer joints at both ends of the propshaft especially if its a midlift - also heard that you can’t get dual clutch on a tag due to the even shorter distances ( though I stand to be corrected on this )