Curly is playing trombone, and properly holding the 2nd brace of the slide. When the slide goes flying and wrings Moe's neck, the 2nd brace is gone.
After the bear attacks and Larry jumps back in through the window; he closes it behind himself, and it stays closed in scenes viewed from the outside. But, all scenes from inside show the window open.
When Curly says the line, "Waiting for the dressing and cranberry sauce", we see Moe beginning to squeeze the duck's beak on Curly's nose, but the picture fades to the next scene before it happens.
A string of spaghetti on Moe's hair disappears when he throws the pasta at Curly.
When Curly is knocked to the ground by a rock, his hat falls off, but it is back on his head in the next shot.
When Curly is seen playing the trombone, he is putting the slide out during the high notes and puts it back in during the low notes.
When Curly is playing the trombone, he moves the slide in the wrong direction for the sound which is produced. When the slide is pushed out, the tone should get lower, not higher.
A wire can be seen on top of the bear as it is sniffing around the cabin, which pulls him toward the window.
When Moe goes over to confront Larry about him eating the plate of potatoes, you can see the set carpenter's chalk scribbles above Larry's head on the wall.
A wire is visible when Curly's trombone slide gets lodged around Moe's neck.
The judge calls Moe, "Mr. Moe." Since they are in a courtroom, it would have been proper to call Moe, "Mr. Howard".