i use magnetic earth radar and it say that i have 0/2 unique item and just to be sure i check and all the chest and hidden item where collect. I have a theory why my seraphine duplicate because when i open the chest the first time i was in my normal version but after that i softlock myselt with the bug with the orb so the nest day i has just put my save in a copie of the game where my noclip was activated just to be able to continue and the third time i was back with the normal version so maybe it cause this chest to be close again but what weird is that all the other chest that i open while the noclip was active where not close or maybe it just the chest just bug i one time and was close by itself.
( I also remember that some normal chest that i open where close when i see them in the game so maybe it just a bug with that.)