During a side mission Saints and Samurais (or something like that), you're tasked with helping someone held captive, but you're asked not to "take any life" by quest-giver. However the mission objective is "kill or incapacitate/stun (I don't play English version) is one and the same, with no non-lethal option as optional and no matter what I do (go in gun blazing with my non-lethal pistol, using non-lethal hacks like overheat or simply using [R] option for non-lethal takedown after sneaking up on enemy and grabbing him) the victim complains that I killed his kidnappers...

Is that a bug just with quest itself or am I missing something?
I had no problem using non-lethal methods on Cyberpsychosis side-quests target and Regina never complained about me killing a target, so I guess it worked as it should?

I have the same problem. I used my "non-lethal" steel pipe and yet enemies dropped dead and I failed the side objective.

i had a similar issue and it turned out i was accidentally hitting one, sometimes more, of the enemies again after they were down and incapacitated which led to them dying.
i carefully went through and made sure all were still alive before finishing the mission, and it worked fine.

When you down an enemy with a non-lethal weapon, they go into what I call an "execution mode". If you hit them again in that state they die.

So, if you swing around like mad with your melee, you'll probably kill them after they go down but before hitting the floor.

I just use the strongest revolver with PAX, that way I know for certain they're down.

I had the same issue in one quest and it turned out that putting a downed, but still alive, enemy into a container let the questgiver think I killed someone. If I just let them lie on the ground everything was ok.

Not to mention you get bonus XP and bonus street cred for executing enemies after you've incapacitated them... game seems to send mixed signals.

I am very intentionally boppin' them once with my weakest melee attack with a non-lethal physical only damage baseball bat and they are very much so dropping dead. I'm even aiming for limbs, torso, etc.

Also playing it on Hard. I think if you oneshot them they just crumple.

Huh, never happened to me.

But then again, I don't use non-lethal weapons as such - when I want to not kill anyone I just switch in my magic non-lethal cyber eyewear, which makes every weapon non-lethal, and that seems to work most of the time.

The only time it didn't was when I took out a cyber-psycho on a railing, and he fell down after going unconscious and then died. ;)

Which quest?

The monk complained I killed people after using a non-leathal gun.

Other quests, putting an unconscious body in a container (cupboard or box) kills them, so for those quests you have to leave the bodies out in the open.

(That's not true. I play mostly non-lethal and there are no complaints when hiding them.) <- Scratch that, seems to happen sometimes.
In some quests targets have to die though and here will non-lethal takedowns via guns or quickhacks count as killing regardless.

Regarding buggy non-lethal takedowns: I'm not sure if this is actually a bug or intentionally, but I noticed that when I use Short Circuit on a target (without downing them) and then immediately afterwards down them via my gun (non-lethal) they will lie down breathing after the fight, but some seconds later (20-30 sec, outside of combat), they will get an extra buzz from short circuiting which will kill them. That happens for me since 1.12 and fucks over non-lethal quests.

Rescuing the guy from the militech compound in the badlands.

I would fail the optional part every time, so I watched for the point it failed. As soon as I put a body in a container the optional "don't kill" disappeared.

So reloaded and left body on the floor and completed the optional park.

Fair point.
Just replayed the quest for testing and yeah, you're right - the objective fails when you "dumpster" them.

Mind you you would likely die if left unconscious in a sealed box in a desert

Ha, real life logic in a videogame? :)

Strange design though that you can "takedown and hide", when the only real option is to "kill and hide" + makes stealth harder since bodies sometimes can mysteriously be detected through walls...sigh

I managed to do that monk quest non-lethally without a problem. Most of those takedowns were via sneak attack, but I'm sure I did a few head shots on at least one of the enemies.
Yeah that seems like a new bug. It wouldn't surprise me if it popped up via one of the patches, since I haven't had issues with non-lethal takedowns thus far (and haven't really tried any lately, so could just be not seeing the issues for that reason).