The ship as depicted arriving in port in England has a different paint pattern on its funnels than the one shown crossing the Atlantic earlier. And, the final shot of the ship docking, the ship has four funnels - not the three in all the other previous shots.
When Cynthia and Bill are on deck in the moonlight, when the shot goes to a close-up on them, there is a noticeable break in the rear-screen projection of the sea behind them on the left of the frame.