Whenever Joe looks out the window from the motel room, the reflection of the motel sign is backwards.
In the scene where Karl and Joe try to get into the vault they use the Clock, it is heard ticking but the second hand doesn't move. Within the context of the series, the Clock's hands are permanently frozen at 1:20:45 (the time that The Event occurred). In real life, the "second hand" on this particular make of clock is not a second hand, but rather an alarm indicator.
After Miller returns from the vault with The Bus Ticket, he hands it back to Wally. When Wally went to place it in his jacket pocket, a bare part of The Ticket rubbed across his finger. He should have been transported to the street.
In the last episode, Kreuzfeld is about to enter the motel room using the Key, and for that he has nailed several Objects to the door. These Objects disappear/reappear from one shot to another.