Auto-run is not broken, but it is a bit tricky. When you want to steer, hold down the auto-run key briefly until you are aimed in the new direction. Or use the mouse to look in the direction you want to go, then tap the auto-run key.

Tapping the auto-run key while in auto-run does not act as a toggle. It changes direction to the direction your character is looking and returns to auto-run.