There was a bug report from 2023 that pointed out exactly the same problem I had today, but it was closed off a couple months later, so here I am reposting an old/new bug report for it.
In the Ruined Era on the Courtyard map, there’s a secret entrance to the Sealed Shrine which has two regular gold chests on either side of the room, and a blue chest at the backend on an elevated pedestal with stairs.
Just as previously reported, nothing happens when you click it, but if you walk off until it’s out of your view and come back, it’s appears open…with nothing on the ground or in the chest.
What I would like to know is if this is working as intended, or if it’s a bug that hasn’t been dealt with?
I guess we’ll have to assume it’s not worth their time to give us any details on the subject matter. It will remain a mystery until a few months from now when someone post another bug report for it.
I just encountered this as well, and as described by the OP. The only thing I can add is that when I clicked on the blue chest, it made the “chest opening” sound before failing to open or providing any loot.