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)
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)
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)
Answer: I guess that 1) the King assumed that Ventress' droids were meant to capture the Jedi, not kill him outright. When she yells at OOM-224 to shoot Yoda, she evidently failed that expectation. 2) Sending out a bunch of Droidekas after it is plain that Master Yoda has clearly won is not a sign of good sportsmanship, either.