A crack separates the metal into two pieces, one on each side of the crack. If load/stress is uneven, force is focused at the end of the crack. This is because that is where the two pieces are joined, adjoining the unequal forces.
Good practice for crack repair is to drill the end of the crack. This will spread the stress to the radius of the drilled hole.
It may be difficult to drill at the exact spot where the crack ends. Maybe drill just past the end of the crack to make sure. The idea is to not leave part of the crack on the other side of the hole. Then JB any sort of close fitting plug to fill the hole. IMHO