At roughly 1:14:25 as the Hun are exiting the caves, they reuse the same shot twice. They film them coming out of the caves, cut to a shot inside, then back outside of the cave. It is the same shot but shorter.
When Kriemhild holds her baby by the fire and Attila rushes in, the angle she holds the baby changes in one shot.
At 19:38, as you see the treasure in the water, you can see a hand in the reflection to the left of the sword. Presumably it was filmed in a fish tank.