[2021] Unable to mercy kill downed Hounds

This bug is really bad, but sadly none of the suggestions here are causing an un-stabable Hound for me. We've seen a bug similar to this one before which was a result of interrupting the Hound while it was using an ability, but we fixed that up.  I wonder if there is now a specific ability, and interrupted at a specific point that could still cause this? Sadly a video of what causes the problem is worth a million pictures of the problem after it's already happened. Or if you're sending in log files, it would be super helpful to add markers so we know where to look: either using the in-game Screenshot feature (F6 key)  or sending a message in Chat both leave a line in the log that we can search for.  ("This Hound's play dead skills are amazing")

I've copied several of your accounts. It seems unlikely to be any specific mod or ability you're using. I tried following the video that was posted however the quality is low and the action is extremely fast so it's not really clear what happened. I did try killing via Banshee spots, by using Viral status, by using Hunter Munitions, and having Hound affected by shield drones during/after the kill.  Nothing bad happened.

However, a log was sent in that might have a clue. Nothing shows up in the log when the hound breaks, but a question:  how many of you are having an no-stab hound where it's the first hound of your game session? I don't mean the first hound in the mission, I mean the first one that you see after launching the game.  Is this only a problem that starts to show up after your Sister has spawned into a mission and you tried to stab her for example? Or maybe the first mission is always fine, but then the longer you play the more hounds become no-stabs? 

Potential cure for unstab-able hounds coming for this in next hotfix, thanks to those that submitted materials to aid in the hunt!