In case of A4 configured as master, you could simply use mute destination option introduced in the latest firmware upgrade, 1.1.1:

In the MIDI PORT CONFIG menu there is now a new option, MUTE DEST, which determines whether track muting/unmuting sends out MIDI CC/NRPN.

This way no need to uncheck all other MIDI options. Not sure if there’s similar entry in the AR menu…