I am having the same issue with Lightroom CC, also running on Mac OS High Sierra.
Moderator: Generated a new discussion
Try to deactivate the GPU support: Adobe Lightroom GPU Troubleshooting and FAQ
The next step is to try to reset the Lightroom preferences: https://www.lightroomqueen.com/how-do-i-reset-lightrooms-preferences/
Do you have installed the latest version of Lightroom (actually version 7.2)
Is your system up-to-date?
From my past experiences with problems 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.
All this sounds drastic and it does take time and effort, but a clean installation can fix many problems.