Same as this report here (https://ludeon.com/forums/index.php?topic=41806.0)
Sent one colonist on a rescue for a single downed refugee & was ambushed by 3 tribal and died. My other colonists received the -8 banished debuff. Completely vanilla, no mods.
Game file (http://s000.tinyupload.com/index.php?file_id=28061188049736464010)
Attached output
[attachment deleted due to age]
Alright i can confirm that...
I reproduced it with 2 nakeds on a Incapacitated refugee quest. Got a Ambush from Pirate Raiders... My 2 nakeds were incapacitated and the caravan was lost...
I got 3 Colonists saying that the 2 were banished to death while it is the complete opposite. They got kidnapped by pirates when the caravan is lost actually and was destroyed...
I Reproduced this with Dev Mode and just spawned a bunch of incapacitated refugee quests until there was danger like an outpost or a bunch of raiders waiting for an ambush there. And made sure that the caravan that i sent was killed or downed by the raiders there.
I've also experienced this when sending one of my pawns on a solo caravan and getting ambushed, having them die in the process.
Interesting. I happened to lose a colonist in a caravan, but it was to plague. By dumb luck none of them were able to tend, although I had brought medicine, so he died. I tried to send one of them back with a muffalo, to no avail, so he was actually alone. My colonists got the -3 penalty for a pawn dying. So the cause of death must matter here, or the type of quest. My guy was heading towards a peace talk, before I split and let him try to get back to base.