I just don't run the Targeting HUD and it doesn't happen anymore (for me) - I still run the Tesla Coils once in a while though, heh. I tried saving/quitting/restarting to no avail. I also may have saved/quit/restarted at some point too just coincidentally if that's worth a shot.
This may not be 'it' of course, but it is something that happened to me in the past. Once I completed Sanctuary I was able to talk to him and continue.
From the site: PC - This can be fixed on PC by opening the console, selecting Preston Garvey and inputting removefac 00075d56. There are some fixes listed there too that may help to resolve the issue. all resulting in a friendly NPC you are trying to talk to, just dying in front of you. This is very similar to a known bug listed on Preston Garveys wiki page. Thus, combining the two, a friendly NPC that you are just walking up to can be Highlighted and then Hostile becoming shocked with the efficient Tesla Coils PA Mod. One way it might be going off, is if it is combined with the Targeting HUD Modification for Power Armour Helmets - this mod will 'highlight' enemies, but can sometimes trigger on friendly NPCs and friendly Robots for some reason - which causes them to become Hostile. If I may state what happened to me (with people 'dying when I approach') you might have on Armour or Power Armour with the Tesla Coils Modification - this armour mod will 'shock' anyone close to you with Electricity and it might be going off on Harv.
