When Peter and Olivia arrive at the home in "Beacon Hill" it is raining yet when they leave a few minuted later, it is sunny and dry.
As Peter is talking on the phone with the person from Chinatown, the phone is in alternate hands on alternate sides of his face with each shot.
When Walter describes his health status after the encounter with the worm, he mentions his "white blood count" being "through the roof". In fact, a very high (through-the-roof) white blood count (above normal) would be a sign of infection.
It is said several times that Astrid was followed back to the lab by the men from Chinatown. This could not be possible as they were already in the lab when she got there.