E.g. when arming_state_changed == true:
First time publish at https://github.com/PX4/Firmware/blob/master/src/modules/commander/commander.cpp#L1194
The second time (because status_changed = true too, see https://github.com/PX4/Firmware/blob/master/src/modules/commander/commander.cpp#L1186): https://github.com/PX4/Firmware/blob/master/src/modules/commander/commander.cpp#L1214

The same story for control_mode.