Had the same problem with Collector and Finisher.
I think this issue occurs if you go back to menu and start a new game (I had to do this cause ended up missing a collectible without knowing that once you go inside the cabin you can't go back out).
So you need to make sure to fully restart the game in case of missing anything else the achievements will bug out.

+1, the same problem with Collector and Finisher achievements
Go them only on the 2nd playthrough

Thanks for the guide. Just a few notes:

-The Collector Achiev is not mandatory, in fact in level 2 I collected one item, then I went back in the hut, so I missed three items and I don't think I can get them afterwards, so I had to start a new game
-You can actually get the Enhancer and Squatter Achiev by zooming and crouching at any time in the game
-For me the Collector and Finisher Achiev were broken on my first playthrough, while I got anything else. Funny that these are exactly the ones which you call "Not missable achievements". But of course that's not your fault that they were broken for me.
Then I restarted the game and played a new game and collected every item without inspecting any of them and (I guess more importantly) completly ignored the steam overlay, so I didn't make screenshots or opened the steam overlay. This time the two missing achievs popped for me.

Thank for checking out the guide.
I can see your point and I updated the basic info of the guide. Hopefully it's more clear this way.

One playthrough is enough to collect all the achievements (it will take around 45 minutes).

Nope. one achievement is about past 60 minutes on the game on one session so.... no less one hour for finish 100% it.

Thanks u for ur guide