When Nate revisits the vault a gun cocking sound is heard as the gun comes into view. When the gun is fully shown, it is not cocked.
When the team is outside the "DC Subway" (which is actually called the Metro) signage for the Flying Elephant Delicatessen and Capital Pacific Bank is visible in the background, revealing that their location is actually Portland, OR.
Sophie introduces Sterling as "Agent Smith" to the lawyer, Reinhold Shecter, but previously Schecter had mentioned that he had talked to Sterling, and it is unlike that Sterling would not have told Shecter his name.
Schecter said that he had known the code to the vault, but only used it when he took people down there - that could not have happened, as it was said that no one except Gault (and, surreptitiously, his son) had seen the painting stored there.