Old Friends Not Forgotten - S7-E9
Revealing mistake: When Anakin says to Obi-Wan that if they do things his way they can help the people in the city now, his hair is blowing in the wind, and the locks by his forehead are obviously clipping into his head. (00:02:42)
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)
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.