Story bugged for me too at the Malevolent Memory . Vortex Crystal is inside the color (it was the red one) and wont take any damage. The Fragile buffs are all inside the instant death fields and Marjorie seems stuck standing in the middle of that as well whacking away at the Vortex Crystal. When I get the color buff I can go in but I seemed to stop doing any damage to MM once I got him down to a certain point and it would not go any further. My hands finally wore out and I gave up.
I too, really do not want to have to redo this all over after having worked so hard to get this far only to have it bug out.
Same exact thing for me, except the buff field was green instead of red.