If the arrow hit one inch behind the shoulder and should have come out behind the last rib on the other side then that is not what I would call "slightly quartering". That sounds like a very hard quartering to you angle. It's not the best angle to shoot deer with a bow. Odds are you caught one lung at best even if the shot is exactly as you perceived it to be. And yes our eyes can fool us about that as well. They can go a long ways on one lung.

I have bought and tinkered and hunted with so many different types of broadheads that it would be depressing to sit down and figure out how much money I have spent on them over the years. On the mech head side I have shot Snypers, Spitfires, Steelheads, Jackhammers, Reapers, Shockwaves, etc, etc,. I have shot fold from the front type, rear blade deploying, you name it. I have never had one fail to open on a target or a deer. And it's not just me. Out of all the friends I have that bow hunt none of them have had any of the various mech heads they have used fail to open over the years either.

So it mystifies me that time and time again the story on the internet is some guy who has bought his first pack of mech heads and has the very first one fail to open. I've heard this story so many times with those exact claims that it just boggles the mind as to the odds it could be true.