Please follow the steps below and try reproducing this issue.
- Open Preferences>Performance Uncheck "Use graphics Processor" and then try importing.See Adobe Lightroom GPU Troubleshooting and FAQ
- Remove all external devices connected to your computer such as hard disk, USB drive,Phone,Tablet and then import.
Let us know if that helps.
I disconnected everything except the mouse and keyboard and followed the troubleshooting suggestions, but still the same. It does eventually complete the import dialogue, but it takes 15 minutes for each step.
Please optimize your Lightroom catalog from File>Optimize catalog and if that does not help create a new catalog to see if that helps.
No joy. As it happens, I had to a complete system install due to a hard drive issue and after that, I'm still having the same issue.
It's worth to try restoring Lr preferences to default following Resetting Preferences in Lightroom CC/6 after you backup your catalog.
This is a known issue on Mac OS sierra when switching to develop module but haven't been reported on Windows OS.Lightroom 2015.7/8: Panels and filmstrip black when switching to Develop macOS Sierra | Photoshop Family Customer Commun…
Also, post your Lighroom>Help>System info here.