I have had two springs go with the end failing this way. It appears that with the ends bent to form a hook or loop, the force of the spring is trying to to uncoil it and this is unnatural and breaks the hook but the actual spring is still in good shape.

You can purchase springs with steel straps at an increased cost or you can purchase a pair a straps for 7 dollars at a garage door place. I am using steel wire rope and associated clamps which I clamp onto the spring coil and feed the wire rope through it. I have done this to the failed part and will do it to the good parts also (garage door up). The failed part is holding well and the forces on the spring are as intended as coil stretching only and not the unwinding stress as experienced with the bent up hook or loop. Your straps should work similar. My springs failed in the cold winter with the springs extended (garage door closed). This probably won't fail for many years so I won't be able to provide any feedback.