In the final scene at the fort, there should have been bodies from the previous battle all over the ground. None were visible.
During the raid a cannon is loosened from its base, turned and fired without being reconnected. Attempting to fire the cannon like this would cause the barrel to fly up, and certainly not fire properly.
There are numerous occasions where handguns are precise at distances far beyond what is plausible, is fired more than six times without reloading and even hit targets they are not even aimed at.
The way the fuse is connected to the dynamite during the raid on the Yankee base, only a single charge would go off. The fuse simply goes around the other charges and doesn't connect to a detonator.
The film is set during the American Civil War. Dynamite wasn't invented until after the war was over.
American flag seen in the background has too many stars for the period.
The dynamite sticks that are mixed with the gold is dowsed in water to make it harmless. This would have no effect. Dynamite does not have to be dry to explode, as long as the detonator is dry.