Nomad Droids - S4-E6
Continuity mistake: During the incinerator scene, there are two RA-7 protocol droids seen. When the first one attempts to run from the incinerator, the one behind it has vanished, only to reappear in the next scene. (00:20:24)
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).
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.