When Hugo welcomes himself to the Stooges, Larry's hat is on sideways, but in the next shot, it's frontward.
When Curly sprays himself with the seltzer water and gives Moe the hand movement, there is an awkward pause because Curly did not know what to do next.
Larry forgets to blow into Vernon Dent's face with Moe and Curly to knock him down.
Before Moe shoves the cake into Hugo's face, he pauses for a few seconds, for some unknown reason.
After Moe takes Curly's cigarette away from him. The cigar he has is smoking even though he never lighted it. This is just another of the Stooge gimmicks for comedic effect.
At the end of the final acrobatic act with the Stooges, Curly gets up, but accidentally falls back down.
At the end, when the Stooges knock out Hugo, when they say "Is that not a Swastika?", it's clear their mouths do not match their words.