Monsters not dying when HP at 0 - Appears desync related

I think i have a glitch where monsters are not dying even though i have reduced their HP to 0. It then appears to require a different skill to confirm to the game that i have killed them. This results in many more monsters still being able to attack me than normal causing numerous deaths.

This is evidence on two characters using different abilities so i know its not quirk of one character causing it.

Things i have tried.
turning PC off and on again
Verifying game cache
full reinstall of game
checking nvidia drivers up to date
use all low graphics settings
using vulken/dx11 and dx12
trying auto/lockstep and predictive network modes
restarted router - 30 second reset
Checked google/forums and youtube for similar issues with no luck.

I have images of what this looks like on screen but not sure how to upload them.