Continuity mistake: When Obi-Wan, Qui-Gon, and Darth Maul get cut off from each other in the corridor and Qui-Gon kneels down, Obi-Wan is standing in the background with his lightsaber pointed downwards. In the next shot, it's pointing upwards. (01:51:45)
Continuity mistake: When Anakin says his last words to his mother, she is closer to the door than in the previous shot.
Other mistake: When the Jedi, the Queen and her entourage enter the hangar before they leave Naboo, only four of them are reflected in the shiny starship above them. The others are not. (00:23:15)
Revealing mistake: When Darth Maul is harassing Obi-Wan as he dangles in the pit, the first swing of Darth Maul's sabre is out of sync with the resultant sparks (very evident in slo-mo). (01:58:50)
Other mistake: Darth Sidious orders the Droid army to kill all Gunguns in the battle in the field, but as the battle ends, the droids order all Gunguns to drop their weapons, and do not kill them. As robots, they should follow simple orders.
Revealing mistake: When Palpatine meets Amidala on Naboo in the crowded scene Anakin is different from the original actor. Seen in the whole scene with his profile and front shot. (02:05:54 - 02:06:24)
Continuity mistake: When Qui Gon is killed, he falls to the floor with his right arm on the floor. The next shot shows his left arm falling and his right arm on his chest. (01:55:05)
Revealing mistake: In the final celebratory parade/ceremony scene, sun/shadow angles vary drastically between shots and a variety of items (flags for example) cast no shadows at all.
Continuity mistake: At the start of the lightsaber fight in the hanger all three go through some large doors and into the big generator room. Behind them a set of stairs have appeared.
Continuity mistake: When Obi-Wan runs towards Darth Maul and Qui-Gon he is halfway down the walkway, but when it cuts to Darth Maul and Qui-Gon Obi-Wan is now at the far end.
Audio problem: When the droid army are marching into battle at the end we hear a marching army, but they're walking on grass and the sound should be muffled in some way.
Continuity mistake: When Obi-Wan is hanging from the ledge in the abyss after Darth Maul knocks him into it, he sees Qui-Gon's lightsaber a distance from him and uses the force to grab it. Between shots, the lightsaber changes position on the floor.
Revealing mistake: In a few of the wider crowd shots during the pod-race, you can make out some oddities. In particular, if you look closely, you'll see the same group people copy/pasted over and over in different places and different configurations in the audience to make the crowds seem bigger. (Slow motion or pausing helps, but is not necessary.) This is actually a relatively common special effects trick to make crowds seem bigger.
Continuity mistake: Sebulba snaps a bit off Anakin's pod and it is left dangling, however in the following scene where Sebulba is talking to Anakin, the part is back in its original position. (00:54:45)
Audio problem: After the transport is destroyed in the hangar (near the beginning of the film) the scene cuts to Obi-Wan and Qui-Gon. The sound of their lightsabers being activated occurs before they even draw them from their belts.
Continuity mistake: When Qui-Gon and Obi-Wan are fighting battle droids in the Trade Federation ship, Nute Gunray says, "I want droidekas up here at once." As he says this, he turns his head, causing the "straps" hanging from each side of his headgear to hang slightly behind his shoulders. In the next shot from behind, they are hanging in front of his shoulders like they normally do. (00:05:55)
Continuity mistake: When the gungan submarine exits the water, you can see water flowing on the force field. The shot later, the submarine is completely dry. (00:21:30)
Continuity mistake: When Darth Maul is fighting with Qui-Gon, only one blade of his lightsaber is on and on the other side there is just a flat end, with no hole. When he fights with Obi-Wan and Qui-Gon in the palace, there is now a hole at both ends. (01:17:25)
Chosen answer: According to "Inside the Worlds of Star Wars: Episode I" by Kristin Lund, they are "laser doors which lock into position in response to potentially lethal power outputs that occur intermittently during plasma activation process" (the fight takes place in a plasma energy processing plant). There are six laser doors in deference to an ancient Naboo legend in which Chaos is held back by six inpentrable gates. As you say though, they're really just a plot device to add dramatic tension to the duel!
Sierra1 ★