I've tried a lot of things, but it happened again just last night on a fresh solo game. I encountered a biker on my way to the trader quest, and I fired a shot directly at his chest with full charge about 4 blocks away while standing completely still, and the arrow went straight through him, I watched it happen and heard it hit the ground behind him. I don't really fire at zombies that are falling or standing back up that often, because I feel like it's a wasted shot due to movement animations glitching out and what not. I have 1,500 hours played on 7D2D and I'm pretty knowledgeable at almost everything in the game, I don't feel like it's an intentional coding to sort of RNG to completely miss a zombie, even with a primitive bow/stone arrow, because I could go outside and make both in real life (I'm a survivalist type person/redneck IRL), and still hit a human-sized target 10 yards away just fine.
I've had it happen with all levels of bows and all levels of arrows/bolts. Excluding explosive/flaming arrows/bolts simply because I think I've used flaming arrows 1 time since playing the game, and explosive arrows I use on horde nights to thin out packs, if I have them.
It doesn't seem to happen often with sleepers, but it does happen once in a blue moon.
I'll try to record it happening and post it here? I'm not sure if that's allowed on these forums or not.