One reason can be a problem with the graphic driver. Please check that you have installed the latest version. If you have buildin a Nvidia card make asure that yiu use the latest Studio version and not the Game Ready version.
Try to switch off the GPU support from the Lightroom preferences and check if that helps to fix the issue.
Go to Lightroom > Preferences > Performance tab > Uncheck "Use Graphics Processor" > Restart Lightroom.
https://helpx.adobe.com/lightroom-classic/kb/troubleshoot-gpu.html
If this doesn't help, try to reset the Lightroom preferences.
https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/
It's recommended to backup your preferences before you reset the preferences to the default settings:
https://helpx.adobe.com/lightroom-classic/kb/preference-file-and-other-file-locations.html
If this doesn't help we need more informations about your environment. Please provide also a copy of your 'System Info'. This can be get from the LrC Help > System Info menu item. There's a copy button in the System Info dialog. Press this button and paste the info into your next forum post.