I'm guessing it's a GPU or RAM error but the glitch stays with the image of how far back in the history I go.
I've only had it once so far, it only showed up when I went to export my library, I had previously exported this image and was overwriting it but it wasn't the only one.
The glitch shows up in both the preview and the exported image.
[Moderator moved from non-technical Lounge to Lightroom Classic CC — The desktop-focused app ]
As you are seeing artifacts on your image may I know is this happening with all the images or just one specific image?
So you have any custom presets?
Which version of Lightroom are you using and on which operating system?
For GPU troubleshooting for Lightroom please follow this link and let us know if it helps Adobe Lightroom GPU Troubleshooting and FAQ
The glitch shows up in both the preview and the exported image
That means the file is corrupted, and you're looking at a drive about to fail, or bad RAM. Back up everything ASAP.