I will patiently wait for environmental people I know to tell the real cause. What I do know is that ECS on hornets or pretty much any aircraft in the Navy are nightmares. I have been on enough troubleshooting goosechases to know that. ECS is environmental control systems, heat, cooling, cabin pressure, and oxygen. I will tell you that the absolute oldest hornets do not have this problem, I worked on them, F/A-18A+ and we used LOX. Save for a few random B variants all other hornets and supers use OBOGS, or onboard oxygen generation system. Tied into the ECS bleed air system like every other thing in the ECS. Take apart entire belly of aircraft is usually step one. I'm sure this will get figured out, root cause is most likely all the good enviro techs squeezed out of service and fifteen years of flying the crap out of them. The rest is media hit piece.