Can't move or copy app files to other volumes
Since installing El Capitan I can't move or copy any app file (including third-party apps that don't need to be stored in the applications folder) to another volume (disk image, hard disk or USB). The process begins but never gets beyond 'preparing to copy' or 'preparing to move', and after this the Finder functions poorly and always has to be relaunched.
I thought that possibly this was related to the new System Integrity Protection utility which prevents system apps and apps installed from the app store being moved around. But I disabled it and it didn't help. This is a problem affecting third-party apps anyway.
I even tried moving an app file using the command line in Terminal, but trying to move an app generates the message that this item can't be moved because it is a directory. I don't really know what this means and freely admit that I'm beyond the limits of my knowledge here.
Disk first aid hasn't found any problems - I haven't had a chance to run a full diskwarrior.
I'm guessing that this is something that shouldn't be happening, given that every attempt I make just results in the Finder effectively freezing rather than getting any kind of alert to the effect that I'm attempting an illegal operation. But I'm reluctant to go for a full system reinstall without finding out first if this is the result of a bug in El Capitan.
Can anyone shed any light?
Using mid 2012 Macbook Pro (retina screen)
MacBook Pro (Retina, Mid 2012)