Settlement merchants refusing to trade after defending settlement

So my settlement traders at Sanctuary won't trade with me anymore after I defended the settlement from the last robot attack. Any time I approach them or try to interact with them they just give me the "Thanks for helping us blah blah" dialog over and over, and no matter what option I choose it won't go away. I've tried moving the vendor stalls, fast traveling away and back, resting until another day, restarting the game, etc. They seem to be permanently locked into their thank you dialog and won't trade with me anymore. Are they cooked or is there something I can do to break this loop?