There is obviously a level of convenience with being able to access the files on the phone from Windows Explorer but if you having trouble with this approach there are other ways to transfer files between the phone and the PC:
1. Use an App on the phone, for example ES File Explorer. You can share a folder from the PC and then use this app to copy files back and forth. I have a NAS and I also use this app to be able to transfer files directly between the NAS and the phone without having to turn the PC on.
2. Use a cloud service as an intermediary. There are loads to choose from: Google Drive, Dropbox etc..
1. Use an App on the phone, for example ES File Explorer. You can share a folder from the PC and then use this app to copy files back and forth. I have a NAS and I also use this app to be able to transfer files directly between the NAS and the phone without having to turn the PC on.
2. Use a cloud service as an intermediary. There are loads to choose from: Google Drive, Dropbox etc..