Other mistake: When Amidala is escorted out of her palace by the battle droids, the droid standing on the right side of the steps has no shadow, but all the other droids and people have. (00:21:15)
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)
Other mistake: During the fight scene in the Theed hangar, several times the droidekas (destroyer droids) are shown shooting, but no lasers come out of their guns. (01:46:40)
Other mistake: When Darth Maul and Qui-Gon are fighting in the corridor filled with rays, when Maul spins around in the beginning of the second shot, half of his lightsaber disappears for a few frames. (01:51:25)
Other mistake: After Darth Maul is killed, in the shot where he begins to fall into the pit, there's no reflection of Obi-Wan's lightsaber blade on the shiny floor. This can also be seen in the shot where he rushes over to Qui-Gon. (01:59:15)
Other mistake: In the ending credits, Keira Knightley's first name is misspelled "Kiera."
Other mistake: When Darth Maul is fighting with Qui-Gon for the first time on Tatooine, Darth Maul's first saber strike actually hits Qui-Gon's hands and saber hilt, not the blade.
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.
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 ★