I have seen this happen multiple times on our ML SUV's around 70k miles. The ends of the spring are subject to getting sand/grit ground into the protective coating where they flex against the spring perches. Once that paint is compromised, winter road salt starts to weaken the spring. Plus, a build up of dirt/grit on the perches holds salt and moisture against the spring and makes corrosion worse. Our's have all broken at one of the ends. Dealer has been clear with us that springs are a wear item. Anyway, not surprised it happens with our E70's as well. On our latest ML, I've been trying to wash that area of the undercarriage better during the winter. Don't know if it will help or not. The British solution would be to make sure your lever shocks leak just enough to keep that area forever coated in oil.