iPhoto not automatically deleting photos on iPhone

When I sync my iPhone to my MacBook Air, I get the expected option in iPhoto to delete the photos from my iPhone after importing them on my mac. The alert window says "Delete Photo on Your iPhone?" and I select the option to delete. Everything seems okay, however, when I select my iPhone in iPhoto, it tells me that all photos have been imported and asks if I want to Remove Photos from my iPhone. I select the option to delete then get another alert window asking me to confirm if I want to delete these photos - I select again to delete these photos then get a progress bar that says "deleting photos", but when it goes away, the top right corner of the screen just says "Loading...", but never deletes any photo from my iPhone.

I have updated to the most recent OSX (Yosemite) and iOS (8.1.2 on iPhone 6 - AT&T) versions, but still get this "loading..." message that never seems to finish and the photos are still on my phone.

Anyone know what I'm not doing right? I still get this when restarting my mac and rebooting my iPhone.