There seems to be a known issue where Iphone files sometimes will not move from phone to PC. One of the solutions suggested in help forums is to changed your iphone setting to "Use original" vs "auto choose compatible" file version. I changed mine to use original and sure enough, different file sizes moved nicely from my iphone to my PC. However, I now wonder if this is a new variable when working with my clips and wonder if this was tested... Or maybe this is nothing.
It seems like when most people have an issue it is with .mov files... but then again iphones must make up half of the VP users.