With a ProfiLux, the Mitras are not slaves of a master Mitras but they are normally all slaves of the ProfiLux which must be the only master.
I'm afraid I missed a step with you, can you confirm that your ProfiLux is equipped with a PLM-PWC card?
This card is essential for the ProfiLux to act as a master with Mitras lamps.
But indeed yes, I confirm that the MitrasLX7, (unlike a Doser SA in slave mode) always respond via myGHL or the network even in slave mode, this in order to be able to configure individual parameters such as maintenance, offset clouds, or sunrise and energy parameters.

Gaël