Does anybody here have an idea if there is something which influences the probability of kidnappings and other radiant quests not given by Preston himself, but given by unnamed settlers?

We know, that the amount of food and water in a settlement makes settlement attacks more probable, and we know now, that leaving food and/or water in the workshop does the same. If you leave a lot of overproduction of water and food in the workshop, the attack chance raises. I watched this - every settlement attacked had a lot in the workshop, and despite having a defense of better than food+water they were attacked. The base chance is said to be 2%, and maximum once per week. This is fine with me. I collect overproduction now, and had not settlement attacks. It is logical too.

But the kidnappings - are there factors for the chance too? What raises the chance for this? I have now in Sanctuary a nearly permanent kidnapping (an unnamed settler has his friend/brother/sister) kidnapped every few days. After resolving it, it starts 2-3 days later again. If I see a guy standing in the middle of the road, I avoid him, since I am tired of this.

Did anybody see something which could influence the chance of this happening? To few guards? The settlement was attacked just once. Or is it simply a bug - despite of the claim the last patch fixed it?

Edit: Latest patch, no mods, did start a new game with the latest patch, no console use (except once with tcl to free the character). Game runs stable and crash free under Win 7.