I meant someone else sent malachite gems to the battle tower (I think before getting the quest, though), and posted asking where the chest was (they had missed it going through the masters chambers) so they could retrieve the gems. They were able to do so and complete the quest.
There may be a difference between the PC and Xbox versions. AFAIK, though, there weren't any additional bug fixes or changes done for the Xbox version compared to the second PC patch. If the problem was in the interface, that could account for the difference, or there may be other factors involved (length of time since getting the quest, or something).
Try emailing support@larian.com, with a description of the problem and maybe a link to this topic (DKS
support page). Maybe with your save they can figure out what caused the problem, and could probably fix the quest, in any case.
