LR 6.9 hangs during iPhone import
I use LR 6.9 (perpetual license, signed in) on macOS 10.12.3.
LR 6.9 [1106920] on a MacPro. Tried it with GPU enabled and disabled. No difference.
Previously, I would use Apple Photos app to import photos & videos from my iPhone 7 Plus, export them as originals to disk, and then import them into LR. That workflow always worked just fine.
Recently, I was experimenting with direct import of iPhone into LR:
1. Go to the Import dialog
2. Plug in iPhone 7 Plus. It shows up as a source
3. Wait for all photos & videos to "load up" before clicking on the "Import" button
After a few hours, I noticed that some 2000 photos & videos have been imported but then the asset count just stayed unchanged for another 40+ minutes. (I'm talking about the number to the right of the "Previous Import" catalog item.) The import dialog only showed halfway done.
I tried quitting Lightroom but it just hung (had to force-quit). Even after restarting my Mac, I keep getting the same hang when trying to import directly from my iPhone. It's 100% reproducible. Any ideas?