Treyarch talks about Black Ops 6 issue when registering player hits.

If you have been playing Call of Duty: Black Ops 6 or even Warzone, you may have encountered a problem that the game has brought about damage registration against enemies. You can aim, shoot, see the hit markers on your target, blood will spurt from the enemy's body, and yet you won't get that kill, as the enemy player will notice you, start jumping and dropping, and defeat you shortly after.

That's not cool at all...

Well, Treyarch is working on fixing this, but we don't have many updates yet:

"Sometimes players observe incorrect blood visual effects when damage was not actually done when shooting enemies in all modes," Treyarch says in the known issues board on Black Ops 6's Trello.

Currently, it's not clear what exactly is causing this hit registration issue, but there are theories. Twitter user X 'Freund' thinks that client-side blood effects (what runs on your PC) do not match the hits authorized by the server, and that this gets much worse when there is lag/desync in your game. 

"Client-side blood may not be intentional, as there seems to be a first blood effect when your client thinks a bullet hit, and then a second blood effect when you get the hit marker. From my testing, Modern Warfare 3 does not have client-side blood effects, and I suspect that BO6 introduced this recently for some reason."

Freund also believes that client-side and server hitboxes may not be aligning correctly, so it is entirely possible that you are hitting clothes and equipment that are outside the hitbox, but still getting a blood splatter for some reason. It should be noted that Freund was experiencing lag while testing the hit registration issue, as they believe this is a key factor in how it appears.

We don't have much of an idea on how this will be fixed and we hope that Treyarch resolves this, as I want to get back to Black Ops 6 in the best way possible!