For Ref 9.02, The LED light has a diode to regulate the voltage and it draws 5V current from the amp board.
So when the amp is drawing power during playback, less is available for the LED and it gets dimmer. In a few cases where the LED diode is out of spec, it could cut off the power to the LED.
Go to our support website and file a help desk ticket. We can send you two new LEDs for replacement. All you have to do is open up the cover to replace the LEDs with screw driver. No soldering is required. Or you can ask your dealer to contact us for new LEDs.