Which operationg system do you use?
Which graphic card do you use? Have you checked if there an new driver version is available?
Do you have installed the latest version of Lightroom?
Do you have tried to reset the Lightroom preferences? -> https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/
Do you have done a clean reinstallation?
For a clean reinstallation I can suggest the following steps:
1) Save your catalog to a secure location.
2) Use the CC Desktop App to deinstall Lightroom (and Photoshop)
3) Download and run the Adobe Creative Cloud Cleaner Tool to remove all Adobe 'stuff'.
4) Open the CC Desktop App and install the latest version of Lightroom (& Photoshop)
5) Restore your catalog.