When The Bat is unmasked and his hood is removed, he has black circles around his eyes. When he speaks in a close-up, the black circles are gone.
When Detective Jones starts firing wildly up the stairs with revolvers in each hand, we can see him shoot three times, then the next shot is of the wall where his bullets are striking. That wall already has seven bullet holes in it. Jones fires all 12 shots from his two revolvers, but we see 16 bullet holes in the wall. And, all are in a tight grouping, despite his wild shooting motions.
After the bank robbery, there is a obvious slot in the "road" where the miniature car travels.
When Lizzie screams after seeing "The Bat" coming in through the window and going up the stairs, Cornelia enters the room and turns the light switch - but the lights don't come on until she's a couple steps into the room.
Detective Lieutenant Anderson introduces himself to Dr. Venrees as "Lieutenant Detective" Anderson.