My co-worker shot a doe last year with a 140gr NAB from a 7RM. Knocked it to the ground. When he went to recover the deer, it jumped up and ran. Scared the crap out of him as he thought it was dead
. Luckily he was able to shoot it as it was running away. First shot blew-up like you described with no penetration to vitals.
His dad had the same experience with an antelope last year. Same 140gr Accubond, same rifle. Maybe a bad batch from Nosler? They are huge fans of the SST, go figure! You can't give them any amount of Accubonds now.
Also last year, my buddy shot a moose with a 150gr Scirocco (factory Rem Premier). He said the bull went down under a tree and just laid there. Buddy thought it was going to die when his daughter said, "It's getting away!". Dropped it with his 7RM. The first bullet hit bone and then veered off at an extreme angle not hitting anything vital. Basically stunned the bull, like the doe in the first example. Now you can't give him any amount of premium/bonded bullets. He's going back to Core-Lokts and will probably never change.
All the shots above were broadside at relatively close range (no longrange shots).
I suspect that weird things can happen when little metal projectiles are moving really fast.