Two Raymarine E120's but only 1 showing scanner info

[svmobert]

So if you swap it back to the way it started, it works okay? It's only if you try to reverse the way it was originally that it doesn't work?

If that's the case it could be something bad in Unit B's radar circuitry, or power supply (internally, or low voltage coming in). If the voltage is too low the radar will have issues working properly.

Otherwise, I don't know the actualy cause of you issue. If one unit works and the other doesn't, same model, same firmware, same cable/radar, etc, then it's likely a bad circuit in the non-working unit.