Striking and missing....

As far as why some snakes have trouble finding the "right end" to start at, I have no idea. One of my snakes starts at the tail end or middle regularly and I posted questions about this on another forum some time ago. The replies I got was that it shouldn't hurt the snake to take it end first but that digestion may be slowed down because of this. What I do is make a simple note in my records about the prey item being eaten butt/middle first and allow a couple extra days for digestion before handling or offering another item to avoid possible regurge. No regurges from this particular snake thus far (knocks on wood). This snake has actually managed to bend the prey in half and swallow it like a ball! Pretty comical too watching him manuever a limb sticking straight out into his mouth as well!
I am by no means an expert but I hope this helps alleviate some of your worries. I hope someone with more experience can offer more on this topic.