Lightroom 6 - "don't import suspected duplicates" stopped working on iphone. Now it thinks all photos are new every time.

The frustration LR gives me is never-ending. 

Import from 2 iphones - previosly it could tell which photes had already been imported when "don't import suspected duplicates" was checked.  Now it cannot.  Even if I manually select new ones, reboot, start again, it sees them all as new - nothing is grayed out as if it already exists in the collection.  I upgraded to LR 6.10.1.  Both phones still see all images as new.  The camera card grays out duplicates as it should.

As if this isn't annoying enough.  I decided. Fine, Lightroom, you jerk, I'll just keep track of the last date I imported and select them manually.  I'll select all the ones after the last date I imported. A pain, but I don't have the time to keep digging into it.  Nope, now LR seems images that were taken on mulpile days all on the same day.  So I can't figure out what day I've already imported.  Metadata is for sh*t.

I thought LR could do photo management, it cannot. Now I am struggling with looking at images one by one to figure out if it's in the collection or not.

Is there a plugin I need? 

Please help.