This issue occurs when Auto Tone has been applied to your images.
For existing photos, select all your images in Grid view, and then click the Reset All button in the Quick Develop panel. Then, click the Auto Tone button to properly apply this feature.
To prevent this issue from occurring in the future, choose Lightroom > Preferences > Presets (Mac OS) or Edit > Preferences > Presets (Windows). Reselect Apply auto tone adjustments.
Let us know if that helps.
Go to Lightroom Preferences
Click on the Performance tab
Uncheck the Graphics Processor