He's having an issue with his hands, he doesn't know what hand to shoot with. He's right hand dominant with the ball and can only really make layups and hook shots with his right, but he writes with his left so he shoots left handed. In reality he needs to be shooting with the other hand.
It's kind of like LeBron, LeBron is naturally left handed but in basketball he's right handed
edit: I'd also like to add that Philly's training staff is trash. Everyone knows the fundamentals of shooting, but they don't make him shoot fundamentally, his elbow is always out, his body is square to the basket, lead foot be off, all that.
He doesn't even practice shooting before games, he just works on drives and hook shots for most of pre-game.