Hi,
i use different file collections, for example one that ist containing files, which are supposed to be copied on a USB stick.
So the collection contains files which are well accessable in normal operation, except when it comes to copying (from collection to the USB stick); selecting all files & dragging them to the USB won´t work, at least that way. An error will show, "sytem can´t find file" or so.
Only when dragging the files one by one it will work properly. So i guess this is probably some minor bug.