1. Make sure you have enough disk space on the device you're trying to move the files to. After deleting files, the problem will most likely be resolved.
2. If that doesn't work, create another file folder on the device you're trying to copy the files to. Then copy the files into the new folder.Sometimes storage devices get finicky if there are too many files in one folder or if the file names are too long. Copying the files into another folder on the same device can get around this issue.

3. Restart your computer, which might free up RAM that is preventing the file from being moved.