I have a Galaxy 5s with a 32GB external card, which I connect to my Windows 7 x64 PC with a USB 2.0 cable. I can copy files from my phone to the PC all day long with no problems. Copying files to the phone from the PC is virtually impossible, however.
I can open the phone's card in Windows Explorer, and look at all the files. But trying to copy anything onto the card hangs explorer. Right now I'm trying to copy a 42MB MP3 file from my PC to the phone - it's telling me "27 minutes to go" and it's already taken half an hour.
I checked this question from 2013 which seems like the same problem, but basically the answers were "you can't get there from here." Was wondering if anyone had a solution for this.