Original post:
I've noticed a recent influx of posts about the game not realizing that characters have a specific item necessary for a quest.
....
Amulet of Bhaal (workaround: you can use Knock on the first door near the Undercity Ruins waypoint, or shoot the corpse hanging over the circle.
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New Edit 1/11:
It's unclear exactly what mod issues (and it looks like now also non-mod issues) are causing the bug, as there have been multiple different fixes that have worked for various people. List of some potential fixes:
Whatever you do, please be sure to be careful and back up your saves -- I'm collating info here in case it's helpful, but nothing here is a guaranteed risk-free fix, and Larian will still be able to give you the best advice.