After receiving the bulk rocket engines I built a rocket as anyone would do. I used a few of the engines they worked flawlessly sent the rockets sky 1000+ ft until the fourth engine from that pack that was faulty and sent the rocket into an uncontrolled spiral where it shot back towards my house and the pyrotechnic charge went off and burned a bunch of our landscaping 5 ft away from our house. I looked over the rocket to make sure nothing was off and I took calipers to the fins to make sure they weren’t warped. Nothing was wrong with the rocket. Which leads me to blaming the engine