Answer

In a redundant system, both designs are running at the same time. If the design uses Command Buttons, both Cores will make a socket connection to the device. This produces double transmissions of a command to a device, which can cause issues if the device can only accept access once at a time.

Solution
The way around this is to send the command through a scripting component, such as Block Controller, Control Script, or Text Controller. These components only connect to an external socket if the Core is currently active.

Refer to the Control Scripting topic in the Q-SYS Help for more information about scripting in Q-SYS.