TBV123-AN - Why do the LCD screens flash blank when power is switched off at source?


I have a switch in the booth on my TBV123 line arrays to remove and apply power, before powering up and down the X32.  When I use the switch, the speakers power up normally but when I power them down, while the X32 is powered up, the speaker LCD screens flash blank a few times and occassionally I can hear a slight clicking in the speakers in conjunction with the flashes. 

The speakers do not try to boot and  nothing appears on the screen, only the LCD screen backlight flashes blank multiple times over 5-10 seconrds before going dark completely. (The number of flashes and duration is never the same)  I have a couple floor monitors on the same circuit, which go dark immediately as expected. All the speakers are supported over Ultranet connections back to the X32 through a P16 Distributor.