When Caleb knocks Daniel out, Ham drops him on the floor with his head near the dining room table and his feet towards the door. But when Caleb finishes the phone call that sets Daniel up, Daniel's body is now turned 90 degrees with his feet now pointing away from the door.
When Diana is holding John at gunpoint at the end, she is clearly using one of the rubber non-hero weapons, as the muzzle of the weapon (which is pointed at the POV) is solid rubber.
When the Earth people are celebrating their victory over the Visitors, the celebrations in all time zones of the world are in daylight which would be impossible.
The doomsday device on the mothership requires the turning of two separate keys to become operational. However, the two keys are kept in the same place, right beside the doomsday control panel. The two keyholes are a few inches apart. And all of this is accessible by entering a single code on the regular control panel. In other words, there is nothing to stop Diana (or anyone who knows the code) from simply activating the doomsday device by herself. A second person is not needed at all.
Visitor officer uniforms display rank in the form of stripes both across the left vest shoulder and shirt cuff. Pamela's uniform erroneously shows 4 stripes on the shirt cuff, but only three stripes on her vest.