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.