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I noticed that they finally added the achievements on GOG Galaxy. So I ran through on Nightmare and unlocked all the achievements. And the "Esteria, we hardly knew ye" achievement won't unlock. I have ALL of the other achievements! Is there an invisible one or something? What gives? I put a LOT of time and effort into this and I feel a bit slighted at the moment.
Hello Friend! So unfortunately this didn't just happen to you, in fact this achievement is broken, and I've already sent a message directly to those responsible for Discord at Xseed Games, who said they are aware of the situation and would resolve it, but that already makes some months and so far nothing has been done.

This is a common issue with achievements that unlock after getting all others. YS II suffers from the same problem.

For more information about issues like this, follow this topic: