After closing 3 void ruptures, I tried killing the Thrax Legatus to end the rotation, but after defeating its physical form, no spectral form appeared. the legatus was still tagged on the minimap and i can hear it, but it's not "physically there". I even used my AOE alt fire on my operator and try to hit anything, but no dice. I had to leave the mission because it's stuck on that "kill the thrax" phase.