I can no longer open the dialogue menu with Preston, which prevents me from taking him as a companion. I've completed a variety of Minuteman quests with him, up to and including retaking the Castle. Now Preston just tends the crops at Sanctuary Hills, telling me how much he trusts me but otherwise refusing to do anything.

A similar problem occurred with Hancock later on. I completed his quest far enough to gain the option of him becoming my companion--I refused, and he pouted and stayed at the State House. I haven't spoken to him since, until I started the Silver Shroud quest, and I'm at the point where I have to have an audience with Hancock as the Shroud, and the conversation won't initialize. I speak to Hancock, and he makes a passive-aggressive remark about me not killing Bobbi No-Nose, even though I did kill her. I can't open dialogue with Hancock, or further the Silver Shroud quest.

Also, in case this matters, I looked at the completed quest objectives for The Big Dig, and the summary says Fahrenheit thanked me for not letting Bobbi steal from Hancock's strongroom. In reality I killed Fahrenheit and robbed Hancock blind, so there's that. That may not be related, but either way.

I've tried reloading and interacting with Preston and Hancock in every way I can think of. I've also tried shooting both NPCs in the face to see if that jogs their memories, but it does not. So this is a thing.