i use the last version of lightroom 6 and i use system MacBook Pro (Retina, 15-inch, Mid 2015) 16 GB core i7 ,, the problem is when i export image from my canon 5Dsr lightroom becomes so slow and i can't zoom in or out and also i can't close it and all image disappear !!
Please follow the below steps.
> Go to Lightroom > Preferences.
> Click on the General tab
> Uncheck “Show ‘Add Photos’ Screen”
> Restart the computer
> Restart Lightroom
Let me know if this helps.