just because it's not hit you in something else using the engine does not mean it is not a standard engine bug. just pick a unity title and google it with "camera will not stop spinning."
anyhow, you may need to fully uninstall the controller.
also, to be clear, /any/ input device can do this outside of mouse and keyboard. this is why i mentioned VR. if you have /any/ other input devices, disconnect and uninstall them.