"The End?" achievement not working

[||☆|| Athal ||☆||]

So I completed the ending (killing the Spire heart) with all the four characters a long time ago and this hidden achievement wasn't completed. I guessed maybe I had to complete ascension 20 with one character or so to debugg it, but today I got the ascension 20 achievement completed with The Silent and "The End?" didn't got completed. Is there some way I can fix this? Maybe start with a new save slot and complete again the ending with all 4 characters? Thanks a lot for your help.

[||☆|| Athal ||☆||]

Ok so I think I actually solved this issue so I'll post this for anyone who might have the same problem or some issue related to this. I wasn't aware that Slay the Spire had their own in-game achievements which are related with each save slot (edit: you can see this achievements at your Statistics section). I just used one save slot, so this was not the problem, but looking at the list I realised that the ending achievement with the warrior-like character was not completed (even though it was completed for Steam). This same thing could affect players having issues with achievement such as "The Eternal One", so be aware of this. Salut! <3