Aren't you supposed to be able to farm those for shielded bladeling eyes?
Messer sells them later on, as well as metaworm gizzards. That said, the eye supply seems somewhat low considering we've added a few new blueprints that use them, so I'll buff the numbers a bit.
I think I fixed it finally. There are no sprites for jet ski npcs with grenade launchers (outside a few exceptions), and some spawned by accident. In the future, if an invisible enemy spawns, if possible check which weapons/armor they have, as that can narrow down the offending sprites.