Are the lights set to raytrace shadows seing as you are using raytracing? If so, adjust the minimum shadow bias to something like 0.2 and the shadows should form properly. Well, that cured it for me when I got that dappled effect. It happened to me in SR2.1 too. If you are raytracing, shadow map size has no bearing on the final shadow. You will still get sharp edges if you don't touch the shadowmap dial.