We're sorry to see the issue with the pixel grid that you see in Photoshop.
We're here to help. Is it happening with all the files, or particularly this file? Did you try to uncheck and check the option for grid lines to see if it makes any difference? Since when is it happening?
Go to Photoshop's Preferences > Performance and uncheck Use Graphics Processor and relaunch the application.
See if it sorts out this issue. If not, you may reset Photoshop preferences back to defaults and check if that helps. Here's the article for the steps: https://adobe.ly/3ceal5t Also, back up the existing Photoshop preferences if you have any custom brushes, action, and workspace: https://adobe.ly/2vNz6FG.