When trying to import an image to Lightroom CC 2015.10 from Pictures on my Mac OS Sierra 10.12.5, when I click Synchronize, the computer freezes and requires shut down/ restart. This happens about every 1 - 6 times that I try to synchronize to import a new image to Lightroom.
The folder I’m trying to synchronize is on the internal Macintosh HD in the Pictures folder. I’m just importing one new TIFF image at a time into Lightroom from a folder that has from 1 to 50 TIFF images in it. It started when I updated to macOS Sierra. For years in the past it never happened. I have not changed my standard workflow lately.