TV Flickering every second or so

D50-F1; Vizio.

I have tried power-cycling, and I've looked through the settings. The TV never goes fully black as it is more of a blinking, is this a refresh rate issue, a power issue? Backlight? I am not sure what to do. The TV is maybe 5 years old, and never had any problems until this week. Any help is appreciated!

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