They fixed the corpse punching issue, but knockout disappears is you kill an enemy with a Melee attack and if you kill an enemy with a charged melee it takes your melee but doesn’t give you the buff. It will if you don’t kill the target though. Please fix.
As previously stated in this thread, Knockout is indeed supposed to go away after getting a melee kill, at least as of the most recent sandbox patchnotes (from early December, if I'm not mistaken). I haven't noticed this new Frontal Assault bug, even as someone who mains that subclass (granted, I haven't been playing much Destiny recently). I'll be on the lookout for it next time I choose to hunker down in PvP for a bit.
The only new bug I've noticed is this apparent state where your primary is unloaded for some reason, though I thought it was just because I'd swapped weapons too late before a match started. But I think it's safe to say I've both seen and heard enough people make comments about it to realize that my case wasn't just an isolated incident.