Cut out the curves using a band saw. Sand the curves on a disc sander, until you are satisfied that the curve is smooth. Use a router with a 1/2-inch round-over bit to round the edges of the steps. Round both the top and bottom edge of the steps on the sides and front of the...
I also have a theory as to why this happens, my guess is that the router can't change direction fast enough or rather that it can't stop abruptly and then start again to make the "sharp" edge and that it sort of just does a continued motion (if that makes sense) and that's why...