So, I am playing with Randy in Challenge mode (threats set at 100%), and I'm at the point when both allies and enemies come in quite large groups. The problem is that, when visitors come to the colony, all of a sudden they start fighting with each other and they end leaving like 60% of them dead or dying on the ground before leaving.
Since I play with 3x speed I can't really see what causes the fight, but I assume that one or more visitors have a mental break and go on a rampage, and the rest of the group just shoots them down. This has happened to me three times in a row, and it is quite annoying: I have to clean a lot of dead bodies from the ground, my colonists' mood suffers from seeing all the bodies, and worse, if colonists is wander around while the fight happens they have a high chance of getting injured, incapacitated or killed.
I am playing the latest (0.6.532) version of Rimworld.
They could be enemies of each other but not an enemy of your colony.
There is only one group, from one single faction
This has happened to me quite a bit on Randy, due to visitors staying too long and beginning to starve. For me, it's only happened when the visitors end up fighting pirates that spawn near them. They all reach mental break at the same time, and the ones that don't die in the firefight wander and eventually starve.
That is exactly what happens, I think it is a bug that prevents the visitors from leaving once they have been fighting: in my games at that point they all scatter around and stay there until they die. I had serious lag spikes for some ten-fifteen minutes due to this problem, until they all got killed or starved.
Heh- I know I saw a suggestion for "visitor housing" yesterday, might be just the thing from keeping those tardy folks from going batsh*te crazy and killing each other. Although, can make for some interesting people-watching for my colonists.
Yeah pretty sure the problem is a mental break. On long games, siege groups break up more quickly by simply leaving dead bodies laying around for them to look at. Sometimes just shooting one of them with an m24 then leaving them alone until their morale decays is enough. Psychic drone events drive everyone nuts too if visitors or siege groups happen to spawn when one of those is going on.
You can monitor enemy/neutral mood with EdB Interface UI Mod (http://ludeon.com/forums/index.php?topic=5258.0), probably vanilla too but I haven't tried it. Basically anything that can push your own colonists to the breaking point applies to non-colonists too, you just don't see it unless they hang around too long.
As for visitor housing, a simple workaround could be a nice big paved tile area where they normally hang out, with flower pots to keep them in a good mood until they go away. A code solution could be to give all non-colonists a morale boost similar to new colony enthusiasm, depending on the event. Or perhaps fix the issue of not leaving when they're supposed to, especially siege groups when they run out of food.