Dear Explorer,
Ah, yes, the old iPhoto with lots of duplicates problem. I remember when I was at Apple, I used third-party software to fix a customer’s iPhoto library – she had around 700GB of duplicates.
It sounds like you may have two issues here. First off, let’s address your issue with iPhoto. iPhoto uses a database to keep track of all of your photos, and sometimes that database can become corrupted. Fortunately, there’s a way to resolve the issue. I’d like to point you toward Apple’s support article that addresses how to rebuild or repair a problematic iPhoto library. Essentially, you hold down option and command on your keyboard and while you’re still holding them down, click on iPhoto to launch it. You’ll be met with a dialog box with a number of repair options. I’d recommend checking ‘Repair the iPhoto Library Database’ and ‘Examine and repair iPhoto library permissions’. Choose ‘Rebuild’ and let iPhoto do its thing. Here’s the link to Apple’s article: https://support.apple.com/en-us/HT201769
Sometimes it helps to start with a fresh iPhoto library, and here’s how to do that: Hold down option (not command-option like before), and while you’re still holding it, open iPhoto. This time, iPhoto will ask you which iPhoto library you’d like to use, or whether you’d like to create a new iPhoto library. Choose to create a new Library and give it a name. Try importing your photos again and see if that helps to resolve your issue.
I mentioned I had used third-party software before to fix a library full of duplicates, and that software is called TidyUp. It’s $30 and it works both on iPhoto libraries and regular folders full of files. I found it to be powerful and about as user-friendly as that type of software can be. It’s not free, but anyone with a lots of duplicated photos will attest to the fact that $30 dollars is a very fair price when weighed against the headache of manually sorting through thousands of photos.
I hope I’ve hit both issues for you. First, address the issue with your iPhoto library, and if that doesn’t work, use duplicate removing software to get rid of the duplicates and then import them into iPhoto.
Thanks for posting and best of luck,
David P.