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 ★