Screen has white vignetting border halo - MacBook Pro, Retina, 15 inch, Mid 2015, Mojave 10.14.6

My computer wouldn't wake this morning. I when I got it to reboot, it came up with this odd while faded border around the screen.

I thought I had booted up to a safety mode of some sort. But the white vignette remains even after a normal reboot.

I've had this computer for many years and have never had this problem. The room is was in stays at a steady temperature around 70-72 degrees.

I have a few thoughts on what is causing this, but none of them seem like a strong correlation:

1. Could it be related to the new power cord I bought (Apple 85W MagSafe 2 Power Adapter) about 10 days ago? But the problem didn't show up until today.
2. Could it be related to the new battery that was installed a couple months ago? Everything has worked fine up until now.
3. Could it be that I update to Mojave a couple months ago? Again, everything has worked fine up until now.

I did nothing unusual with the computer last night than I usually do. Left the top open and started the screen saver. I've been on Mojave for a few weeks now with nothing like this happening. There were no power outages last night.

There's another thread here from August 2020 where the person mentioned shutting off the computer for 30 minutes made the problem go away. I'm not sure it's necessary to shut the computer down as the vignette does seem to be going away very slowly as I've prepared to type this.

Even if it goes away, I'm curious what would cause this?

Anyone else have this issue?