Thanks for your Feedback. I am afraid, reboot does not help. I deleted and re-installed Textastic, then I deleted and re-installed Owncloud, and then I wiped the iPad and did a clean install. I have absolutely no idea what to try next.
just to let you know: I have the same problem. This happens not only with owncloud, but with other document picker enabled apps too, like e.g "working copy".
With Textastic I get errors like "...konnte nicht nach file12345566676754320 bewegt werden, da letzteres nicht existiert, oder der Ordner nicht existiert."
With Byword it works fine. So it looks like a problem with the temporary file names.
Btw. Thanks for your good work! Apart from this error Textastic is an excellent App!
Customer support service by UserEcho