[Solved] Can't complete settler rescue mission

[Harmonica]

edit: I finally managed to complete this quest hand-in and get my reward and clear the mission log. First my original problem, the solution is in my second reply:

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One of my settlers got kidnapped by raiders and taken to the Ration Facility. I cleared it out and saved them. Hilariously they were one of my supply runners, so their Brahmin was there in the base with them. I don't know if that caused an issue during leaving, since she did not have her cow with her when we left the base (the cow got lost in the base or ran anyway or something).

When we left, I followed her thinking she was going back to the settlement, but she just seemed to walk around seemingly at random. I left her and went back to the settlement to finish the quest, but the quest giver doesn't give me the usual cut-scene mission completion. He just says 'well done and thanks' etc. Nobody else seems to even know about it either.

I've tried traveling away and saving and reloading but I can't get the mission completion dialogue to trigger.

Has anyone else had this issue and solved it?

[Harmonica]

Some more info after trying some things:

The settler is no longer named as a provisioner, just settler.

I can kill the settler to end the mission with failure, before or after rescuing.

I can kill the quest giver to end the mission with failure, and aggro the entire settlement...

The text in the quest has not changed from 'I need to rescue the settler' even after rescuing her (I think it should say 'I need to return to the settlement..'), even though the step is now 'report back to x'.

The settler that got kidnapped is not from the same settlement as the quest giver. I think this is the probable cause of this bug, if it's a bug. She was a provisioner from another settlement. I know this because if I kill her, the settler count from that settlement drops, and the supply line disappears.

Anyway, I don't want to kill her or the quest giver.

Maybe I have to wait til she returns for the correct completion dialog to be available? It seems like the game still cares whether she lives or dies. I just wish she'd return to her settlement.

[Harmonica]

Yay. I finally got this mission successfully completed!

I tried multiple things to get the proper dialog to trigger from the quest giver, but none worked, so I went off and did another randomised quest (defending a settlement from attack), and then just went to my base and built some stuff before sleeping. After sleeping for 10 hours and waking up I got the failed mission screen, meaning somehow I was still on a timer. So I reloaded for one last attempt at triggering it.

I walked direct to the quest giver, woke him up and talked to him. Still no mission success. I slept at the location until morning. When I woke up and walked to him, I see that the rescued trader is returning with her brahmin! She arrives and enters the settlement, and I speak to the quest giver. And finally get the proper mission dialog! I also got to speak to the rescued settler (now listed again correctly as provisioner) and she thanked me again.

The only thing that I tried in sheer desperation, the night before, was to assign the quest giver first to the settlement where the rescued settler was really from, and then back to the current settlement. Did this unbug something? I don't know.

I think sleeping in the location was probably the key thing, since it let events trigger on time because I was in the location. The settler wasn't living in that location, so I had to wait til she arrived on her route to get the actual dialogue. By sleeping there I guess I caused her to spawn in as a provisioner again. Or maybe I just got amazingly lucky and she took that long to walk back, and I was able to speak to her before the quest expired... either way I'm glad that is over.

If anyone ever has this problem, hopefully this information will help you solve it, couldn't find any info anywhere else online!