If your arrow weighs 525gr or more....you're likely pushing enough KE to shoot mechanicals.
Sure, the shot was bad, but the reason I found the arrow is it only penetrated less than an inch, then fell out when the deer ran by a fence post.
I think I could put a rubber suction cup on the end of my arrows (with the speeds they're traveling) and get more penetration.
Something isn't jiving, here....and I don't think it has a darned thing to do with the BH choice. You say you found the arrow. Was it deployed at all? Why didn't it? Was it stuck?
TOO many people using today's Mech. heads with NO issues for me to abandon them for(or lend much credence to) these horror stories of old.