Okay. Alloy nipples are more brittle and more prone to seize up and that can cause them to crack if deformed as your tension the spokes. If you can remove any tire/tube/rim tape/strips and take a small bottle of silicone oil, like maybe a 10 - 20 Wt. SAE equivalent in approximate viscosity (and use silicone based oils so it's more benign to rubber), and apply a drop to the base of each spoke seat/rim eyelet from the tube side of the rim. I use a high quality fishing reel oil. Then add a drop where the nipple threads onto each spoke and let sit for a few minutes. Then tension your wheel to recommended specs for the rim. But if you've had failures already, and it's likely that more will follow. If you feel inclined, you may want to swap out the nipples yourself with new nipples made of nickel plated brass.