Many forget that especially at distance a deer can raise its head, lower its head, step sideways, forward or back in a split second, which is enough to make a good shot a poor shot! Now you have a wounded deer.
How right you are! I've killed more than a few deer that surprised me by "twitching" between trigger pull and impact. For me this usually resulted in a neck hit even though the sights were dead on for a dbl lung shot. I know they twitched because the entry wound was on the "opposite" side of the critter.