Could you please let me know the exact version of Lightroom installed on your computer ?
Also which MAC version are you working on ?
Did you try :
- Go to Lightroom > Preferences.
- Also please Go to the Preferences > Performance Tab, and uncheck "Use Graphics Processor "
- Restart Lightroom and see if it works.
I will try that and get back to you.
I am using Lightroom CC on a Late 2015 Retina 5K 27 inch iMac
That seems to have solved the problem.
You are Welcome, Glad to help.