quest bug report

welcome.
I have a character (Sourcer) and I'm stuck on the mission in Valley of the titans, the mission with the 2 medallions.
I have the 2 medallions, I found the altar where I need to put them, but the moment I press the "I" key to open the inventory to put the 2 medallions, that small window where you have to place them actually disappears. I did this mission with another character class and it worked.
I can't go further because of this mission.