While doing the ‘Technical NOGout’ side mission, during the second wave of bad guys while defending Quinn, he ran into the pool of corrosive liquid, to the far left of his workstation.
After I had cleared the area, I went to find him. Each time I would try to revive him, he would come back to life, and then die again.
The only want to resolve was to Fast Travel out of the world, and back to Sanctuary. Once I appeared back there, the mission status changed to ‘Collect Reward’.