The carrot in Curly's shirt pocket disappears and reappears during the sequence in the junkyard until they enter the bank.
The cobwebs on Curly's hat disappear when he sees the X mark on the wall pillar.
When Curly grabs the can full of coins and runs off with Moe and Larry to confront the lady and her young brother, he grabs the can with his right hand and holds the can behind his back. When he is shown confronting the lady and her brother, he is now carrying the can in his left hand.
When Larry lights the fuse to the dynamite, the end of the sticks are flush with the wall. As the boys are trying to get out of the hole, the camera views of the dynamite shows the sticks protruding several inches from the wall.
The President's office is shown as being in the Capitol, when, in fact, it's located in the White House.
Gold is a very heavy metal--11 ounces to the cubic inch. In fact, this is illustrated when Larry tries to stuff gold ingots in his pockets and his pants fall down. However, there are a great many gold ingots on the small table--with thin legs--in the middle of the room in the Treasury vault; the table does not appear strong enough to support all that gold.
Moe's stunt double shows his face when Larry pulls him out of the wall.
When the cop says "Get 'em out!", Curly can be seen mouthing the same line.
Curly's line "It attacked me!" is clearly dubbed.
The boy has only one crutch that he is seen using on both sides. The first time he's seen, he's using it under the wrong arm; he should be using it on the side with the bad leg.