I tried to explore most of the island before I touched the actual story content and wound up getting the mechanical parts for Hogarth and Westport a while ago in my save. Now I'm back at Westport and have convinced the three people to leave but have not been able to trigger a conversation with Hogarth. I even tried sabotaging the three facilities afterwards and the only thing that changed was some of the town npc chatter mentioning the most recent sabotage. I'm almost 20h in and would rather not have to restart the game from the beginning just for a single side quest.

yep, same, If i give Hogarth the parts, i cannot talk to him any further. I had only spoken to the tech, the purple mouth guy, and not yet the doctor. I also only sabotaged the radio station. But if i give him the parts and complete that quest, he just doesn't open any dialogue selection interface, he instead repeats the same phrases about how the parts will help. I want to complete both quests, the mechanical parts and the brainbenders quest. but it seems like i have to pick one or the other, and have the rest stuck in my quest queue permanently. very annoying if you want to try to complete all the quests.