When they were at clients home, I focused during the day.
When I am working on it at my place, I have focused at night and come up with similar scenario (focused at night).
I might not have mentioned it before, but I temporarily replaced the domes at the clients with 79G Bullet IR cameras and the same fog effect occurs. So it cannot just be reflection off dome cover. Maybe reflection off a wall.
But, again, when I brought the domes back here, I was able to recreate similar effect, that is worse with cover on, but is mostly remedied by turning down the low light luminescence seting from .75 to .25.
I picked up Hunts better dome that is WDR and 650 lines in both an IR and non IR version that I hole to test here tonight.