Lightroom 2015.8 Release crashes when exporting files

I take photos everyday and after processing in Lightroom I export selected photos to my Mac (late 2015, macOS Sierra 10.12.3). Every 4th or 5th attempt to export photos results in Lightroom crashing. This is the sequence:

1. In Lightroom Library I select the flagged photos.
2. I choose File and then Export.
3. Under Export Location/Export To/Folder, I select "Choose" to identify the export folder.
4. At that point I get a continous spinning progress wheel. It doesn't stop.
5. I then have to choose "Force Quit" and Lightroom is highlighted as "not responding."
6. I force quit Lightroom.
7. I attempt to restart Lightroom and it is unresponsive.
8. I have to reboot the Mac in order to get Lightroom working again.
9. It will allow me to export photos 3 or 4 times and then the issue occurs again.

Any suggestions for fixing this issue?