Because of the phasing issue with the succubus NPC Sensiria once you reach a certain point in the questline you are unable to pass 43/45 quests in Feralas for the achievement. A really simple fix would just be to bump the requirement from 45 to 43 and anyone who’s actually after the achievement will be able to get it.
I’ve completed every single available quest in the zone, the ones I am blocked from getting are due to that NPC phasing away once you hand in the other questline. What I’m missing → The breadcrumb quest to gain entry (1) and the two given by this NPC (3). There’s been no word on this and I’ve talked to several players having the exact same issue. They’re stuck at 44/45 because they did the breadcrumb quest to get in, but are stuck on the exact same phasing issue.
Edit the file, change a 5 to a 3. Problem solved. I’ve made a ticket about this in the past as well but gotten the usual “marked as resolved” automated response with no results or human interaction.