Question: Can't backup iPhone photos to PC
For years, I've been able to easily backup my iPhone photos to my external hard drive by having both connected to my PC laptop, and just copying from one device to the other. However, that's suddenly not working. Now when I try to do this, particularly with larger files, I get error messages such as "A device attached to the system is not functioning", or "The device is unreachable". I think these messages are applying to the iPhone, but I can see its contents on my PC anyway, I did tell the phone to "Trust This Computer", and my external hard drive is also fine.
What is going on here, and how can I back up these photos to free up space on my phone? My iCloud is full (and those photos won't download, but that's another issue I'll deal with later), and I've always preferred manually backing up to my external drive anyway. Again, this has worked for years...
iPhone X, iOS 11.3