Freezing, not responding, Mobile Footage

I've been editing footage from my Iphone recently since I've been having to run-and-gun certain shoots.

Usually, I have absolutely no issue editing the 4k footage after I import it onto my computer. However lately if any of the footage is over 3 minutes not only does it take longer to import but it bogs down the process so much that I can hardly even edit on the timeline. 

I'll play and then try to pause it and the visual display won't change and I won't see the timeline bar moving, but I can HEAR the audio continuing even after I click stop. 

I've attempted to make Proxies and even that hasn't worked. 

Please help 😞