could be a chest or the mephit ambush... also perception is one of Astarion skills so go get him and come back to take another look
On early level, Astarion and Shadowheart both have +3 in Perception. Astarion has proficiency bonus (+2 until Level 5) and +1 Wisdom. Shadowheart has +3 Wisdom.
However, after the ASI at Level 4, since Shadowheart is a Cleric (class that uses Wisdom to cast), Shadowheart could have +4 Perception (while Astarion is still at +3 total).
Right past the first chunk of mithral ore (after the animated armor), there's a perception check that I just can't make. I tried enhance ability, guidance, and several reloads, but can't do it. Does anybody know what it's for?
In addition to what you've listed, try and take your character(s) with the highest Perception skill (not Wyll or Gale) in priority.
Every characters get to roll the dice I believe. So sometimes, I would go to camp and switch companions. It was sometimes quicker then reloading OO
I don't have any better advice than that, I'm afraid 😅
Good luck (literally)!