If this symbol appears it simply means: under voltage.
1. Be sure that the USB devices you have connected to the RX is not drawing too much power from the unit. An externally powered USB hub would be recommended if you have multiple USB peripheral devices connected to the device.
2. Also, be sure to use the power adapter used with the unit is the original provided with your unit.
Even when the warning may appear, this usually has no adverse effects unless the voltage is too low.
REV 11/19