Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - Bugs & Technical Problems Splitscreen Camera Issue

Had this issue too, just found the following thread and it fixed it for me: https://steamcommunity.com/app/435150/discussions/0/3223871682610473849/

In short, the solution was to launch the game with keyboard control, go into Options and reset the keyboard mappings to default. Quit and re-launch the game and use the controller.