masking sliders glitching out

Hi @TeodorsLapsa, Thank you for reaching out, and welcome to the community!

Please share an exact description of the problem along with details like your workflow and system configuration. From Help> System info> copy and paste it into a text file and attach it with your response. Does this happen with all types of image formats or just certain ones? Also, when did you start noticing this issue? Did this start occurring after a significant change, like an update of the OS, after installing a plugin, or after any hardware change in the setup?

While we wait for your response, please try these suggestions and see if they fix anything.

1) Resetting Preferences can help resolve various issues and return the application to its default settings. 

• Quit Lightroom Classic completely.
• While holding down the Shift + Alt keys, launch Lightroom Classic.
• A dialog box will appear asking if you want to reset your preferences.
• Select "Reset Preferences".

2) Try turning off the GPU in Lightroom: Check out this article for steps and more information. Troubleshoot GPU issues | Lightroom Classic

Let us know how it goes!