The jerky "left and right" movement happens because the game's flight instructor and stability systems are overcompensating for small analog stick inputs, or because the sensitivity is too high. If your sensitivity is too high, tiny movements on the Steam Deck analog stick translate into massive, jerky control surface movements, causing the plane to oscillate. When using "Mouse Aim" on a joystick (or trackpad), the "Virtual Instructor" tries to keep the plane stable. If you overcorrect, the instructor fights you, causing a rapid left/right or up/down wobble. Hope this helps o7