Cannot progress "Legacy of the Vaal" quest

I'm stuck at "Activate Two Generators" quest in Jiquani's Sanctum.

I activated both generators, then started fighting the boss, the game crashed.
When I logged back in only one of the generatos was enabled and I was not able to find another Soul Core.

I've reset the instance 2-3 times, still I find only one Soul Core and can't activate the instance.