I have been attempting to download my purchased movies to my Synology NAS drive. However, I keep getting a -21 Error immediately after clicking download on most of the movies. I do not get this error when downloading movies to my hard disk on my MacBook Pro. I don't know what is going on, but it is very frustrating. I want to have a physical backup of movies that I have purchased.
iMac 24″, macOS 15.3
-21 Error
The macOS error code -21 is an IO (input-output) system error, likely related to device communication or read-write errors. Could it be unsupported folder permissions? Could it be that other processes are interfering (e.g. backup) at the same time?
I don’t have this particular NAS, so others may be more familiar with any errors that might occur.
Can you do a Finder copy of the download from Mac to NAS, rather than a direct download on the NAS? Then you can try deleting one and re-linking the other.
Downloading purchased movies to a NAS using TV app on iMac.
