This is going to be either a software failure or a hardware chip failure.
The first thing to do is a soft reset by unplugging from AC for at least 10 min. If that fails do a hard reset, look at your manual for that.
These TVs are known for this, due to a eMMC chip failure apparently. These sort of circuits are known as flip/flop circuits. Capacitor failures in these type of circuits can cause the problem you are having.
If a hard reset does not solve it, I don't think there is anything else you can do.