Factual error: When examining the sand, Bobbi states "According to carbon dating..." Fitz finishes by saying "It's a billion years older than the earth." However, carbon dating is only good at determining the age of something to about 60,000 years old. The only thing carbon dating could tell about the sand is that it is 60,000 years old or older. It certainly couldn't determine that the sand was 5 billion years old.
Continuity mistake: After the interrogation, Skye tells Agent Coulson about Agent Ward. Coulson says during this scene,"It's a magical place" and Skye says "Ward doesn't like your style. Kinda think I do." At the end of this line, Skye is looking at Coulson. In the next shot, she's suddenly looking 90 degrees in the opposite direction.
Continuity mistake: In the scene when Coulson is using a diagram to explain to the team that Cybertek is the common denominator of everything that's happened during the season, he starts tracing lines that connect various bubbles of the diagram to each other, ending with one that links "the bus" to "GH-325." In the next few shots that last segment suddenly disappears, only to reappear later on.
Continuity mistake: When Daisy is hugging Jemma after proving they're both human, Daisy's right arm is hooked entirely around Jemma's neck. There's an angle change and a lens flare (possibly to help cover the cut) and Daisy's right arm is now at 90°, with her hand on Jemma's left shoulder.
Continuity mistake: In the opening of episode 20, Coulson meets General Talbot in a saloon that is a secret entrance to their hidden base, a base that is many stories underground. Yet in episode 22 Coulson uses his robot arm to call another jet; it appears outside a window! He can't have a window in his office, if the base is several stories underground. And to verify it isn't a "video window" or "projection screen", Mac throws a chair through it, essentially saying "We are above ground, let's go get in that jet in front of us."
xx:xx:xxM Edward Lovett
Continuity mistake: When the Watchdogs destroy the government facility near the start of the episode, 6 shots of Nitramene are fired onto the building's exterior before it implodes. But moments later when Coulson calls Mack, he (Coulson) is watching the news report of the event, and the 6 shots of Nitramene are nowhere to be seen.