Missing human?

[DarkSepho]

I've just followed a guide to get all the humans and I should have got all of them (can't tell for sure because I've collected some during the story, but checked every location), but the achievement didn't pop and I didn't even receive the last buff on Rider's Mercy. So I checked around Maker's forge and I can actually count 20 of them.
What am I missing?
Do the humans in the forge actually correspond to the ones you save? Has anyone listed them so I can check which one is missing eventually?

[Crimsomrider]

Might be best to follow this video and check one by one where you missed any. There are timestamps in the pinned comment to make it easier to search.

https://www.youtube.com/watch?v=meFgprsTqgk