Several of the Shimano front der have screw-in pivots (I am pretty sure the Sora does as well) Looking at it from the back you should see two socket screws(3mm) with large heads. Make sure they are tight. If they are even a little loose it will let the cage sit at a poor angle. Once you tighten them they should stay that way. I have seen this enough times that I tighten them when I build a new bike.