Revealing mistake: When Leo is laying his dead kids on the grass, the little girl keeps moving her eyes and breathing.
Revealing mistake: In the very first scene, when Teddy and Chuck meet, they are standing on the bow of a ship traveling at full speed (as the Captain wants to return to the mainland before the storm hits), yet their lapels don't so much as flutter. Even at a slower speed, there would be some movement from the air as they passed across the water.
Answer: The bandage is a symbol indicating when and when not Teddy is caught in his delusions. When the bandage is on he is delusional, thinking he is the marshal finding out all the dark secrets of the facility. When the bandage is absent he is lucid and aware of his past crimes and his own delusions.
Wrong. It's on the whole movie until he takes a shower. The bandaid is off but yet that's the scene where he runs in the lighthouse thinking he's the Marshall still. Did you watch the movie at all?