Revealing mistake: When Achilles stabs Hector, you can actually see the sword vanish from Achilles hands just before the shot switches to the side view of the killing.
Revealing mistake: When Achilles is dying and saying farewell to Briseis, when the camera is facing Achilles, you can see the netting on Briseis's wig underneath her "hair". (02:29:25)
Revealing mistake: Just after Achilles slices Hector's spear, Achilles spins his shield then positions himself behind it. In the next shot facing Achilles, as he starts to walk toward Hector, he does not hold the usual handle on the underside of his shield, instead he holds a small solid handle (used for spinning shield) which is beside the normal handle. Also notice the hilt of the sword is the wrong direction near his elbow, whereas in the following shot when he holds the normal shield handle, the hilt of the sword is properly positioned. (01:59:20)
Revealing mistake: When Hector and Paris return to Troy with Helen, in the first shot they pass through the gate and head down the long path through the city. Then later, when the soldiers head for the armory and when Hector walks through the gate for the face off with Achilles, the path is substantially different. The statue and actual buildings' positions, the curve of the road, etc., are completely different. (This has nothing to do with camera angle.) (00:27:40 - 01:57:00)
Revealing mistake: When Agamemnon finds Briseis kneeling, while Troy burns, he pulls her up by her hair. As she lifts her left arm up, the beige undergarment she wears is visible under her arm. From the moment we see Briseis kneeling, throughout this entire scene, the set lighting and shadows change quite dramatically in consecutive shots. (02:27:05)
Revealing mistake: In Achilles' tent, while Achilles tells Briseis that she is his guest and not his captive, the distinctive tan lines of the actress' bikini top are clearly visible as Achilles holds her. (01:37:15)
Revealing mistake: When Hector and his men are fighting the Greek army outside Troy's walls in the second battle, blood spurts up from the bodies lying on the ground, after "Apollonians! Now!" is shouted. It's very obvious that the blood does not come directly from the bodies. (01:21:25)
Revealing mistake: After Menelaus is killed the two armies clash. In the second close-up of the men fighting, when a Trojan slams a large club-like weapon into a Greek's face, the club end bends when blood spurts everywhere. (01:18:20)
Revealing mistake: When the Greek's rampage Troy, a Trojan falls through a thatched roof. In the next shot a light haired Trojan male is thrown on top of a black haired male, and are attacked while they lie atop a stone landing. Then at the start of the following close-up, a lone light haired female falls to the ground from that very same stone landing, which is followed by a repeat performance in close-up, by the light haired male of the previous shot, with some differences in this take. (02:21:15)
Revealing mistake: When we fly over the beach and see all the ships with the arriving troops, some running ashore, the CGI men look like they're running on the water's surface rather than through it, as they're making no splashes.
Revealing mistake: When the soldiers of Greece are collecting the wood for the Trojan horse, you see bits coming of the wood, revealing the white Styrofoam used to make the wood.
Answer: He was warning the other soldiers that Achilles was coming.