Red U-Net lights are flashing.

Red lights can only be the result of incorrect audio routing. Possible reasons include:

1) Two devices are sending on the same U-Net channel.

2) A device is receiving on a U-Net channel that has no transmitter assigned to it (in other words, it's listening but nobody is talking).

3) A device (i.e. a UX8800) is transmitting and receiving U-Net on the same channel.