I’ve just tried your suggestion (I couldn’t wait!) I transferred the files back to the iPad after deleting the cubasis app and I got my old project back on screen. It played ok but had audio files missing. It had the edit cubes in place but no audio in the cubes themselves.
I restarted the cubasis app and now it won’t load again, doing exactly the same thing as before! Displays the opening cubasis logo page then just shuts down as if it had never been opened.
I run windows 7 on my laptop and could find no folders you’ve described in the users folder. I clicked on my username and there’s no appdata folder in there 
Even more confused now!! 