Dishonoured low chaos question?

So im trying to play dishonoured as low chaos or clean hands as i can but i've noticed there are some deaths at the mission summary and i don't know how its happening. I only choke people or use sleep darts and usually i check by putting the arrow over them that they are unconscious and not dead. I usually lift t he unconscious bodies up and hide them - by putting them down not throwing them against walls or down stairs or anything and i always check to see if there are rats because i did see one time rats eat someone i had just left lying. I've just finished a playthrough for the waverly boyle quest (I choked her and gave her to the guy) I sleep darted 2 maids and choked some guards and hid them in rooms and i sneaked up on weepers and choked them before i entered the party yet it still says 1 civilian dead. I have a feeling it may be a survivor i came across with a guard - the ones who are near the tallboy - i choked both the guard and the survivor without detection and hid them in a building and i know there were rats outside so maybe they got him. Apart from that I'm not sure what im doing wrong - if you pile bodies on top of each other can that cause a glitch where the bottom ones are dead or can dropping a body on someone kill them?

Basically need some advice on someone who has had issues with unconsious people dying or maybe i should just stop choking every person i come across