Currently my Shadowheart is not following anyone in the group, but everyone will follow her.
It seems picking up a dead companion and adding them to anyone's inventory is the cause. Resurrecting them in any way after doing so has them permanently bugged.
Upon googling it seems repetitive sneaking and ungrouping can be another cause for this bug to trigger.
I have tried all possible fixes that worked for the EA version of this bug (Travelling, reloading, dismissing, long rest, death by chasm, jumping, sneaking .ect) but none seem to do the trick for the full release version.
Seems reloading a save prior to picking up their corpse is the only solution currently.
However my earliest save is just after I picked Shadowheart up, and before I revived her. Reviving her in any way shape or form has her bugged, and in some cases, has her T-Posing on the ground too.
I have reported this to Larian but have not received a reply yet, as I'm sure they're very busy with support tickets.
Anyone found a way to fix this yet?