Strange Graphical Glitch - Anyone Know Why?

[alexwukoson]

I've noticed some strange glitches recently. Images becoming pixelated messes, Netflix occasionally flashing a green screen during playback . . . Not sure if they're related though. I'm not very computer-savvy, so I was hoping someone here could help.

Attached are a couple examples:

 

[DeltaMac]

Which Mac do you have?

Did you try reinstalling High Sierra?

 

[alexwukoson]

I haven't tried re-installing. I actually don't know how to.

 

[DeltaMac]

Boot to your recovery system (restart, holding Command + r), which will have a menu window. One of the choices will be to Reinstall macOS.
But, most folks would download the current macOS High Sierra installer, through the App Store.
The installer app will download (it's more than 5GB, so will take some time). The installer automatically launches when the download completes. Quit the installer, and use one of the methods to create a USB bootable installer.

Apple has steps for reinstalling the system here.
another method that works well, is to download one of the apps that makes that process simple, such as DiskMakerX.

You could also run Diagnostics on your new Mac, just to see if any hardware problem is reported.
Restart, while holding the D key. Follow the steps to run the test.