But, the situation took an unexpected turn. Today, I tested the map several times for the probability of such an occurrence with caravans, and it turned out that the caravans are not the cause, but rather the consequence.
The thing is that around the second week, there were two heroes in the main Orc castle again. So, they were just sitting there and switching places at the entrance, but they weren't leaving the castle. Then a third hero ran up to them, but since the first two couldn't leave the castle, the third hero just bumped into them, just like the caravans.
I can't understand what's going on. Perhaps Ment was right about the AI mod. I also moved the torches from the entrance a little further away, but since this bug appears intermittently, I don't think they are the cause. Although today I will remove them and see how it will be without them.
Now I will test without the AI mod; it's interesting why the Orc AI is acting so strangely...