Spokes with insufficient tension break in the "J" bend at the hub flange due to excess flexure. As mentioned above, this most often happens to the spokes on the non drive side of the rear wheel because they are normally the lowest in tension. This condition can be somewhat improved by increasing the tension on both sides of the rear wheel. On 8, 9, 10, and 11-speed wheels I normally set the drive side spoke tension to the maximum recommended by the rim manufacturer. This usually allows the non drive side spokes to have enough tension to avoid breaking and at the same time have the rim centered (properly dished).