Sometimes mac has a problem while deleting or copying a file .If we trash finder preferences (~/Library/Preferences/com.apple.finder.plist) it fixes the things. Unfortunately Apple hides your library folder now so you need to:
- switch to Finder
- hold the “option” key on the keyboard
- Click on the “Go” menu
- Select “Library” (hidden if the option key is not down)
- locate the folder “Preferences”
- locate the file “com.apple.finder.plist”
- move said file to trash
- log out
- log in
- test to see if fixed