Newish TV One has changed from HD to SD/4:3 ratio 480p all by itself

Question

Sometime last night the set top box setting changed from 16:9 1080p  to 4:3 480p.

So I no longer have HD on my HD TV.

Here's what I've tried:

Menu -> Settings -> Audio&Video -> Video Settings ->

TV Type

I select 16:9, but it won't stay on,  it will only stay on one of the 4:3 choices. It will NOT let me set the TV type to 16:9.

Video Format

I select 1080p, but it won't stay on that selection because of the bad tv type setting

I've rebooted the TV and the box, no change.

SD overide is off

HDR is disabled.

Tried TV input control on and off.

I'm out of ideas and I hate calling support.

Conan04 · Accepted Answer

It's a 5 year old 48 inch Vizio, 4K. 48u-D.

And it's running through a Yamaha receiver. TSR-400.

But I found a solution.

Menu -> Customer Support -> Top Support Tools -> Fix Fios TV Issues -> Set Top Box Auto Correction

This starts a reboot and when it came back up with was fine. 16:9 HD with /4K . All like it was the day before.

I had done a pull-the-plug reboot but that didn't fix it. I guess their reboot goes a little deeper.