Deliberate mistake: As the Wraith "stun bomb" activates at the SGC and everyone falls to the ground, it is visible how everyone uses their arms to dampen the fall.
Head in the Clouds: Part 1 - S3-E7
Deliberate mistake: Adrian walks outside the Obelisk Blue dorm to see Chazz standing on a glass platform held up by four cables on each corner, which are attached to a helicopter flying above. Adrian then realises he is standing on a glass platform, held by cables and attached to a helicopter. There is no way he wouldn't have noticed this; he should've seen the cables, heard the helicopter and felt the glass platform beneath him when he walked onto it, even if it makes for a cool reveal. (00:12:55)