Hi,
I'm not sure if I'm missing something.
In forgotten sanctum I cleared the majority of the library first, then the collections. At the bottom of the collections I chose to use Tayn's scroll, then when I exited after killing the Memory monster, neither Tayn nor Llengrath were in the main hall. They were in the scriptorium but at that point neither had relevant dialogue. I simply moved on and cleared the rest of the DLC main quest. After being spit out and resoling dialogue Tayn remained but has no options to let me turn in the quest.
I have it in log on the "Return to Tayn" step. Safe file attached.
