So I'm on an Ion with a 4 rack CEM3 system and everything seems fine. I go to change a dimmer mode and I see racks 2-4 in the device list but not #1. So we go to the rack and move on. Show runs fine 2 days and we reset the same way.
Next day I get a call from the head electrician. He can't change the mode for a dimmer in rack 4 from the face panel!?! Something he does fairly frequently. So he goes to the console and it works fine.
There was some major work here 6 months ago, but things have been fine AFAIK. It's a large site with a complex network that's been subnet-ed for this space.
IP mask is the top of my list to investigate. What else?