Endings Trophy Glitches (Nameless Puppet)

[Slug]

After beating the game and getting the rise of p ending I noticed in my achievements tab on steam that I never got one of the hidden achievements (Nameless Puppet). But as you know if you get this ending, you have to beat the nameless puppet in order to get there. Apparently a lot of people have been having problems with the trophies on steam for this game. I just wanted to know if there have been any solutions. I'm in the middle of ng+ and am planning on getting the other endings so i'm not too worried yet but i just want to know if anyone else has also experienced the same or similar things. Also if they're any solutions to this or if its stuck forever.

[J. Carmine]

yeah i got the same bug, I got the other ending where you fight nameless puppet as well, still didnt get it.

[Poyzo]

I beat Nameless Puppet a few hours ago and it unlocked for me.

[NyaRu]

Me too

[BBQ]

Had the same happen on my first playthrough.
Most likely you defeated the boss with a fable art or deadly attack after stagger. There is a bug that does not pop the achievement if one of those happens. Fight and kill it again but this time with a "normal" attack and the achievement should pop.
This is not exclusive to Nameless Puppet but can happen on other bosses too.