The Japanese sailor gets taken away by the Tanaka family hidden under a tarpaulin. The tarpaulin is roped and the load is well distributed in the back of their truck. When the two boys, Duke and PeeWee, cycle after the truck, you can see that the load is skewed and the rope is in a different position.
This movie takes place in 1942 when there were only 48 states. The flag that is shown at 36:24 on the DVD as Duke Cooper is seen riding his bike into the driveway of his home shortly after Matsuo Yomma saves him from drowning, is of the 50 state era.
The Japanese sailor lies asleep in the derelict factory and the kids approach him cautiously to see if he's alive. In the first shot, he has his left arm down by his side. In the second shot, his arm is draped across his body.
At 00:30:21: When Duke Cooper falls off a balcony (on a set at Lacy Studio in East Los Angeles) into the water (on location in Marina del Rey), a brick wall coming out of the water on the right side of the frame shakes and bends.