@eunyove that definitely sounds like a backlight issue (possibly inverter circuitry on power board or the panel itself). Since this is a pretty new TV I would not even think about opening it without first checking any warranty status.
We have a chance to guarantee our right to repair electronic
equipment—like smartphones, computers, and even farm equipment. This is a once-in-a-generation
chance to protect local repair jobs—the corner mom-and-pop repair shops that
keep getting squeezed out by manufacturers.
Join the cause and tell your state representative to support Right to Repair. Tell them you believe repair should be fair, affordable, and accessible. Stand up for your right to repair!