Red Square inside a universe box

Hi All. I have finally gotten around to building my racks up. I have 3x en4, 1x en12. I noticed on one of then that there is a red box that comes up and looks like it has paused or holding dmx values. What is it? I will try and get a picture next time I am near it. After a power cycle it seems to work again and the red box has gone away. Is it meaning it has lost data? or getting errors on ethernet? Not 100% sure if it was set to artnet or sacn.

Red outline means that universe stopped sending to the node. e.g. unpatched, console down …