I used to believe that until my 300grain TBBC fired from 375H&H failed to break scapula of a cow Water Buffalo.
I was certain of the shot, it was as easy a shot as one can hope for when hunting. Stationery, undisturbed animal, short distance, solid rest against a tree and plenty of time. I knew I hit it well and was stupid enough to trust the one shot. I didn’t follow up being certain I’d find the animal dead within short distance inside the paperbark forrest. The guy who was with me watched the impact and confirmed the shot was true. We were both rather surprised to find but a few tiny droplets of blood instead of the dead buffalo.
I hit it the animal square on the side from about 50m away. The projectile failed to penetrate the bone, ricocheted approximately 90degrees and ended up in the gut cavity. I caught up with the animal the next day, killed it and simply could not believe my eyes when I started searching for the projectile to understand what had happened.
I’d suspect a poor projectile over the caliber in what you are describing. Not saying a heavier caliber isn’t going to do more than a lesser caliber, however for a client I don’t see the need 99% of the time, a PH is a different story.