Q: iphoto is getting stuck when transferring my photos from iphone

This is the second computer I use to transfer my photos from my iPhone to my mac. It stops importing and I don't know what to do. Prior to this I tried on my other computer and did not import all the videos, some of the videos had an "error -54"

I dont understand why is this happening ? I have lots of pictures and videos and I needed to free some space on my iPhone.

any ideas why?