When Simmons activates the pulse that knocks out all of the electronics in the area, Yo-Yo's robotic arms still work perfectly.
In the diner at around 8:20 Coulson is holding the soda in his right hand. When the scene cuts to Daisy it's on the table and not in his hand.
At 8:17, while Phil and Daisy are talking in the Diner, the bottle of the sleeping agent is on the table next to Daisy's right arm. At 8:21 it is gone, reappears at 8:32, and disappears again at 8:39.
The team is supposed to be in 1955, but cars parked at the diner are later models, specifically a 1956 Bel Air coupe, a 1957 Nomad four-door wagon, a 1957 Chevy wagon (blue car), and a 1956 Chevy (black one on the right)
Area 51 is located in southern Nevada. There are no rolling green hills there. They would be surrounded by mountainous desert.
The team determines they are in 1955 from an ad on the radio for "the new 1955 Thunderbird," but they could be wrong, as the 1955 Thunderbird first became available in September of 1954.