DIAGNOSIS: The OLED display panel or its power supply is failing. This is a known hardware issue. It is not a software or settings problem.
FIX: There is no user-serviceable fix for a failing OLED panel. You must contact Levoit customer support for a warranty claim or replacement. Have your purchase receipt and serial number ready.
IF THAT DIDN'T WORK: As a temporary workaround, you can control the purifier entirely from the VeSync app on your phone. The app displays all the same information (mode, fan speed, PM2.5 level, filter life) and allows full control.
HEADS UP: Do not attempt to open the unit to inspect the display. This will void the warranty and presents a risk of electric shock from internal capacitors.