Opening a file using file app or the “Open or import File” button in the hub causes the read only warning even when opening a file that has already been copied to the iPad directory. It is read/write though, so the warning is misleading.
Opening the same file (as a recent file) from the hub does not cause this to happen.
Yes, we’re aware of this one. Sorry for the inconvenience. The warning appears because the URL we are passed by the system when the file is opened from the Files app (which is basically what the picker shows) is different enough to confuse Dorico into thinking it is coming from another location. This is on our list of things to address in due course.