Split jerks are so much more technical than a lot of people realize, and they end up neglecting to pay appropriate attention to technique, footwork and body positioning. There are countless exercises you can utilize to improve your split jerk, and Camille Leblanc-Bazinet has two really good ones.
The first one is called tall jerks. Start up on your toes, the bar resting just above your head, arms engaged. Quickly drop into your split and pause there before recovering. This should be done at a light weight.
The second pause jerks can be heavier, depending on what you normally lift. Pause in both the dip and the catch, focusing on keeping your position and a tight core.
Main image: Camille-Leblanc Bazinet/Instagram