Why does the controller tell me that there is another controller connected to the same DALI line?

If you see External Commands Heard (and you do not have third party devices sending dali) or Other Controllers Detected in the issues list there is a very good chance that you have two controllers connected.    

If there is a link between 2 controllers, performance will be highly degraded and you may experience addressing not functioning and other strange behaviours.

Once an external commands heard issue is set, it will eventually expire if you remove the connection, but you may opt to reboot the controller to force this to occur faster.

Scenarios

DALI->DALI

If a installer inadvertently connects a line to two controllers, the controllers can end up fighting for control causing line noise and unexpected operations.

Note: This notification is limited to those faults where the Positive and Negative terminals of one controller are connected to the Positive and Negative terminals of the second. If the polarity is crossed the fault may not be detected or may be detected as an overload or short circuit.

Wireless to DALI

If a device that is bridging dali devices to a wireless network also has its bridge connected to a dali controller, a similar effect will occur.

Wireless to Wireless

If both controllers are commissioned to the same wireless network.

Signs on the monitor

On wired controllers, you can see the commands sent on the by external devices by their command type prefix.  If they do not have _LCM (ie 16BIT_LCM), they are from an external device (controller / third party unit).