I figured this one out!!!
As you make your way to the ‘Underground Thicket’ there is an elite monster. This monster is the missing Animus carrier.
It doesn’t turn into an Animus carrier until the zone transition into the ‘Underground Thicket.’
The issue is that you can kill the elite before entering the zone triggering the Animus quest which causes the animus to drop. Current workaround is to walk fully into the next zone before killing anything at the bottom of the stairs.