This type and location of break usually happens when the radius rods are adjusted tightly AFTER the lower A has been tighted to the chassis. The A is bevelled on the bottom so it can rotate on the chassis. You should adjust the radius rods first, while the A is loose at the two bolts connecting to the chassis, THEN tighten the lower A bolts so that the A arm is not in a bind. Probably, when you tightened the lower A first, it was put in a bind as you adjusted the radius rods. Just my thoughts, it could've been just a rough track or a hit to the wheel !!