Continuity mistake: Satine and her guards along everyone else who entered the shuttle at the end of the episode disappear - you can easily see inside the shuttle and through the other window.
The Phantom Apprentice - S7-E10
Continuity mistake: Rex, escorting a captured Gar Saxon, is holding a pistol in his left hand when he stops because he sees where Ahsoka and Maul are fighting on the underside of the city dome. In the next shot, when he points at the fight and orders his men to get the gunships, he's holding a pistol in his right hand instead. (00:23:05)
Continuity mistake: When Obi-Wan duels Grievous on the bridge of his Arquitens cruiser, the cyborg General slashes up several computer consoles with some of his four lightsabers. Later, when Obi-Wan sends two clone officers to the bridge to try to detach the ship, the consoles are in the background with no visible damage.
Revealing mistake: When R7 goes to plug in to the socket to look up information on Fives, he moves right in front of one arm of a droid charging station in the room which should be in front of him. (00:16:32)
Revealing mistake: When the battle droid commander orders the tanks to stop because they can't go any further into the forest, the fingers of the droid nearest to the camera clip through the wall of its tank. (00:07:49)
Continuity mistake: When Ahsoka tells Rex to go to the briefing, the rectangular pouch thing attached to the right side of his breastplate is missing. (00:09:24)
The Phantom Apprentice - S7-E10
Continuity mistake: During Ahsoka and Maul's duel, just before she kicks him through a wall, he's pushing her down with his double-bladed lightsaber while she's resisting with her two lightsabers. In a shot from behind her, she has one blade on each side of the handle of his lightsaber, but a close-up of her shows both of her blades on the same side. (00:20:19)
Old Friends Not Forgotten - S7-E9
Continuity mistake: When Cody is telling Obi-Wan about the tactical droid remaining out of sight, the armour accessory he wears on his back is missing. (00:02:05)
Continuity mistake: Rex's kama is missing in a long shot of him and Ahsoka during the hangar bay firefight.
Continuity mistake: When Ahsoka runs out of the medical bay, Rex's kama is missing. (00:01:18)
Continuity mistake: Throughout the episode, clone troopers are wearing armor with four different types of markings; some have none, some bear the markings of the Coruscant Guard, some bear the markings of the 332d Company (Ahsoka's unit), and some bear the markings of the 501st Legion. However, at the end of the episode, the memorial in which clone trooper helmets are placed on their graves, only helmets with no markings and helmets with 332nd markings can be seen, none from the 501st Legion or Coruscant Guard.
Continuity mistake: When Yoda arrives at Korriban, the wings of his starfighter open up when he flies down to the planet. However, in the second shot of him flying down, the wings are closed. (00:01:10)
Nomad Droids - S4-E6
Continuity mistake: At the end, when R2-D2 and C-3PO are reunited with Republic forces, Master Plo asks Commander Wolffe if he knows these droids. However, Plo previously encountered R2 in both "Rising Malevolence" and "R2 Come Home" (the latter episode having the same error).
Continuity mistake: When Rex is giving orders to the heavy cannons after the super-tanks emerge, his kama is missing.
Continuity mistake: Rex has a bandage on his left arm for the entirety of the episode after getting injured in the previous one. After Aayla destroys the probe droid, in a shot of her, Ahsoka, Rex and Bly walking over to the destroyed droid, the bandage is missing. (00:07:11)
Old Friends Not Forgotten - S7-E9
Revealing mistake: When Rex hands Anakin The Box with Ahsoka's lightsabers, his right thigh armour piece briefly clips through his kama twice. (00:12:58)
Revealing mistake: When Ahsoka and Rex walk onto the bridge of the Star Destroyer, in one shot the right part of his kama is partially transparent, revealing his thigh armour beneath it. (00:08:05)
Old Friends Not Forgotten - S7-E9
Continuity mistake: When Ahsoka and Rex watch from their gunship as another one is shot down on the approach to Sundari, his kama is missing. (00:18:24)
The Phantom Apprentice - S7-E10
Continuity mistake: When Ahsoka, Rex and Bo-Katan are watching the evacuation, Rex is holding his helmet under his left arm. When the three of them are going inside as Bo remarks that the occupation cannot last much longer, Rex is suddenly empty-handed. (00:13:27)
Old Friends Not Forgotten - S7-E9
Continuity mistake: When Bo-Katan storms the throne room, the pistol she's holding in her right hand is kicked out of her hand by one of the supercommandos. However, when she goes to fight Almec, there's a pistol in her right holster despite her not having had time to retrieve the weapon. (00:23:30)
Answer: Dooku never accepted Ventress as his apprentice, as far as I know; he just kept her as his devoted personal assassin. In Phantom Menace, it is stated that there can be only two Sith at a time, to prevent a power struggle in the lower ranks. To accept Ventress as an apprentice, Dooku would have violated that rule.