Snakes DO miss, more than once too for the same prey item.
It's safer for the snake to eat pre-killed rodents. I had a friend with a gorgeous boa that ended up with a very upset rat. The rat had a good bite or two on the snake. The snake ended up needing to visit the vet due to the bite and ensuing infection.
Lastly, the owner had to force feed his boa because it came "food shy".
There's no benefit to feeding live except for the owner. A snake is in confined quarters and doesn't have a chance to necessarily move away from a rat if it's body is blocked due to a container wall, as you have already noticed can happen.
I used to feed live, and I stopped that eons ago, it wasn't worth risking my animal's safety for my selfish entertainment and interest.