In the Knicker of Time! - S6-E5
Continuity mistake: When Ash says, "I should be thanking you," Brock is absent, but in the next shot, he appears. (00:00:46)
In the Knicker of Time! - S6-E5
Continuity mistake: When Nicholai notices that May and Max are wearing shorts, Max's brown shorts turn blue like Nicholai's. (00:04:13)
In the Knicker of Time! - S6-E5
Continuity mistake: After Nicholai introduces himself, the bottom of Max's shirt changes from green to yellow. (00:04:43)
Answer: He is a good guy but just found himself in a bad situation when he worked for Lysander. He didn't want him to harm Ash and his Pokémon when he was trying to get the special bond between Ash and his Greninja to work. He does leave Lysander and go back to being a good person.