Can't Find Solution For Broken Quest "The Hold Out"

Every time I do "The Hold Out," Uncle Ken bugs out and repeats the same dialogue, while the quest breaks and won't advance. I always have to reload many times and cross my fingers, hoping that it eventually just "works," but this time it has been hours of reloading and the quest won't progress. Edit: I mean during the "Defend the Visitor's Centre" stage, which I can't ever get to progress, even after killing all the raiders.

I can't find any mods that can fix it, and there isn't anything I can find online about it (although there used to be, I'm not sure where it all went.)

I'm just trying for a last-ditch solution in here before I give up. I'm on Xbox, which is why using the "console" isn't an option.