I'm struggling to think of how it could possibly be due to an electronic fault.
My best guess would be: If there is play in the suspension that lets the afflicted wheel move backwards and forwards in the wheel arch then it will steer the car one way on throttle and the other way under braking due to a change in the caster angle. A sloppy top strut mount could allow this, as could a joint that hasn't been tightened up properly.
If it were my car I'd grab each front wheel in turn and go bananas yanking it in all directions looking for any movement. I'd repeat with the car jacked up and the wheels off the ground, which would also allow me to grab the top of the strut and give that a shake. I might also chock both sides of the front wheels and get an assistant to drive the car into chocks while looking for any lateral movement of the wheels. The trick would be to spot any difference between left and right side of the car.