A New Land! A New Adventure!! - S6-E1
Continuity mistake: When Professor Birch gets Treecko's Poké Ball, another one is upside-down, but in the next shot, it is upright. (00:16:59)
A New Land! A New Adventure!! - S6-E1
Revealing mistake: In the English dub, during the "Who's That Pokémon?" segment, part of Lanturn's tailfin is cut off. (00:11:39)
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.