This incident happens regularly on the Woven Echo “Bountiful Wilds” - the one where you can claim “loot, fit for a great Primalist”.
There is a mod called “Revives after two seconds” - When the monster type “Draal Lava Keeper” has this mod, they revive with all their animations broken. So they still attack with their fire spray attack, but they lay dead on the ground.
This has happened to me on multiple characters across different settings - On SteamDeck, very low graphics, as well as on my 7900 XT on Ultra Quality. As far as I can tell, it’s 100% reproducable.