Arriving on the Amethyst, Flight Lieutenant Fearnley is blown to the deck, falling with his feet in the air. The shot changes, and he is fully prostrate instead.
Twenty minutes into the film, Leading Seaman Frank (William Hartnell) is blown to the deck, losing his cap. He replaces it, only for the cap to slip and be replaced again. It falls off completely as he crawls down the frigate, yet it is on the sailor's head moments later after a shot change.
During the final scenes when being fired on, HMS Amethyst is travelling to the right of screen and the pennant number on the ships side (F116) is mirror imaged (flipped or reversed shot).
When the Sunderland takes off going between the Yangtse and the batteries it would only have been able to do that if it had reversed up the river.
When Consort eventually signals that she's having to give up the rescue attempt, she's still heading up stream yet, when Amethyst eventually escapes and reaches the river mouth there's Consort waiting. .
Towards the end of the film, shortly before Amethyst rejoins Concord, we see a scene with Kerans standing on the bridge of Amethyst. The scene in the background is obviously a still image painted on the background. The waves are static. There is, however, light smoke which is moving between the bridge and the sky.
Landscapes seen adjacent to the Yangtse are clearly far more Suffolk than eastern China.
When Lt Cmdr Kerans is approaching the Amythest, he looks at the damage through his binoculars. The Union Flag is upside down. Although flying the flag upside down is a sign of distress, this is probably how it was unfurled at the start of the action which would have been incorrect.
When Lt Cmdr Kerans is approaching the Amethyst, an officer on Amethyst looks at him through binoculars. The angle of the binoculars view is incorrect.