Every time I go to buy concrete from Connie she's missing… Kidnapped again... been at least five times now! Anyone else run into this and solve it?

Maybe she likes it?

Yeah sorry not sure at all about that.. How much concrete are you buying? I find that after a few days loot and enemies get restocked to locations I {Cleared} and the stuff is free for me to load onto Dogmeats back and pack home.. Well free with some bullet expenditure on occasion. Good luck with the kidnappers sounds like random bad luck or they figured out that you are building a concrete castle and there is some decent caps to be earned by holding her hostage.

Stupid radiant quests are stupid.

Pretty much this. Stay away from Preston Garvey, he is a menace!

That they are.

Have you tried adding more defense? Generally, I set my defense to about twice the population of the settlement.