iMac photo's glitches when connecting iPhone 6

I'm trying to transfer photo's from my iPhone 6 to my iMac via USB, but when I go to 'Import' on the Photo's app, not a single photo comes up and the loading wheel in the top left says: 'loading 0 out of 0 assets'. I then tried Airdropping a couple photos to my iMac and it crashed, I had to restart it. So I think there might be a corrupted photo or something. Has anyone had this issue and/or a solution for it?