During a recent show we had two mics occasionally dropout. The other two were extremely stable.
All four receivers are rack mounted together. We believed all settings are set the same but noticed the two stable receivers had a T and square box in the top right of the LCD screen while active.
I see no reference to this in the manual except for when channel scanning - indicating XD-V70-class transmitter already on and using that channel (or other Line 6 wireless systems operating in RF1 mode)
We did the usual checks for antenna placement, connector wiring etc. It is just the icons which we are unsure about.