I stopped using buckshot many years ago after tracking a buck hit 6 times at about 20 yards - my buddy was right beside me and we both unloaded on him as he ran out of the brush - for a mile and a half following a trail that looked like someone pouring blood out of a bucket. Every 25 yards there was a lot of pink foam where he coughed it up. His entire ribcage was shredded.
If you tracked a wounded deer that far,then that tells me you were pushing him WAY too soon. Shoot then sit for an hour then track. Even if the wound is not instantly fatal he won't go far. He'll go just far enough to feel safe and lay down to bleed out. If you push him then he'll keep running until every drop of blood is gone.