HELP - Cruel Act 3 Large Soul Core Quest Bugged, preventing progression

I killed the boss in Jiquani's Sanctum. He dropped the large core. I got the quest completion. I went back to NORMAL difficulty, same spot in questline to kill a different boss in same map to get the +10 fire res. Killed the boss again. Accidentally dropped the first soul core that I got in cruel difficulty.

Went back to cruel difficulty - but now the stone altar is bugged. The quest says to go back to infested barrens and activate the stone altar, but when I do, I get the animation but then the core disappears and the waterway doesn't clear. So I'm stuck.

HELP. I've tried rekilling the boss in both normal and cruel, but the soul core won't drop again. I tried resetting the instances on the maps. Nothing has worked. Is there a way to reset the questline?

i cant find the soul core in jiquani machinarium to open the door, i think the map is bugged, I re-searched more than once

Exactly the same problem here i can confirm

I have the same problem, my idea is we join someone's game as they are putting the stone in their altar. However, I have come to find that if you already have the stone in the altar, the water will be gone even if you are in the other person's "instance". This leads me to believe that if two people, each with their own soul core, then they each need to place the core in the altar to make the water drain.

Long story short, believe we are all screwed, hope someone has a fix.