Uranus - Stephano Rescue target drown or randomly die

[Sedyana]

I was running Stephano (Rescue) on the planet Uranus.  A very quiet run, no alarms and very few mobs, world on fire on as many may do.  I gave the rescue target my sidearm and jumped into the water for a brief moment.  Once back out I made sure he still had my sidearm and started running along as usual.  2 seconds later the mission fail pops up, the guy didn't bleed out or die, he just went missing, his entire lifebar on the left side just went missing entirely, there were no monsters around anywhere.  Did he fall in the drink? Despawn?  Seems quite buggy