you can try to send a bunch of files with one having a funky character in the name to a fat32 usb thumbdrive it always works... or rather fails!Oh boy. Well, over Christmas I will have a look. Expecting a little shop of horrors.
What's the best error to trigger? Obviously a disk full destination is easy to set up. But that would fail to fail if the file manager is smart enough to check available space beforehand. Pulling a USB stick while the transfer is rolling? Permission errors?