Bug with Luminiferous: Lighting the hidden tower and Mystery of the hidden tower

[coso.9173]

I thought I was doing the achievements wrong, but today I checked and something is not working right.

the hidden tower in Bjora marches has 3 lighting puzzles. I just did all of them, opened the 3 chests (I can even see them now, open and empty) but the central chest never spawned. and it didn't count either for the mystery of the hidden tower achievent, or for the luminiferous - lightning the hidden tower achievement.

is there a bug with this? I have the screenshots of the 3 open chest and the empty space in the center, just in case. :/