When Axel is painting over the port hole window, the amount of paint on the window changes between shots.
When Smitty tries to escape the boat, he picks a box. When he picks the box, he is wearing a jacket with buttons on the sleeve, but he's not wearing a jacket or shirt with buttons.
Ole is standing while the flute is being played, next shot he is seated next to the flute player, next shot he is standing at the railing again.
Aboard the Amindra the deck cargo of oil drums sound empty and move around during the fight. In addition they are not lashed down with cargo netting making them a hazard to the ship and crew if they sail through rough seas.
Newspapers in those days took a long time to typeset by hand and so are compiled and printed at night for early edition delivery to readers, so it would be impossible for a ship that departed the night before to be in the headlines as torpedoed in the morning. In addition, wartime censors may not even allow such a story to be printed to keep the enemy from knowing the name of the ships they sank or their cargoes.
At the beginning of the film, when Driscoll sneaks back to the ship, he jumps from a rowboat into the water and climbs up the anchor chain. The next time onscreen, he appears dry from head to toe.
Wilfrid Lawson's name is spelled Wilfred in the opening credits, but is spelled correctly in the end credits.