Maybe you got a low-quality part that caused it to crack. Also, ensure that the armorer wrench is set at a 90° angle to the torque wrench. If you are sure to keep the 90-degree angle, then you need to buy new bolts. Many stories on the internet now specialize in selling building materials. But I recommend you to buy bolts here
https://www.scrooz.com.au/, because this online store has long been in this area and, most importantly, sells bolts of quality metals.