'Insufficient permission' while downloading a torrent file.
It seems one of the problems here is with the latest system update from Chrome and Apple.
You may have to check your download destination files in you torrent app. Make sure they don't have a 'minus' next to them. If so, redirect them again to the necessary folder. On some torrent apps you may have to relocate your preferred download folders on the torrent app to another location.
This is also an issue with external drives.
MacBook Pro 13″, macOS 10.13