[KoopaOne]

Hi Guys,
I am running a new Macbook Pro M1 since last November. The last few months it worked as a charm using an USB2-Hub.
Then suddenly i had a corrupt db on the Kobo (which i never ever had before, not on windows, not on linux).
I did not manage to get it to work again, so i factory resetted the H20.
Now it runs again, but whenever i transfer books to the Kobo, it looses connection to the Kobo. Sometimes on the first book, sometimes on the 5th, but i didn't manage to transfer more than 10 books i a single command.
Since i have more than 1500 books to transfer due to the factory reset mentioned, this is a bit of a hassle.

I am running Calibre 5.28 with Kobo Extended Plugin
Kobo is on latest firmware

If i am not transferring books, i can keep the kobo connected, it never looses the connection - the problems only start when transferring books. Any ideas?

The error is always:

'OEBPS/Text/Titlepage.xhtml'

Traceback (most recent call last):
  File "calibre/gui2/device.py", line 89, in run
  File "calibre/gui2/device.py", line 595, in _upload_books
  File "calibre_plugins.kobotouch_extended.device.driver", line 400, in upload_books
    return super(KOBOTOUCHEXTENDED, self).upload_books(
  File "calibre/devices/kobo/driver.py", line 2137, in upload_books
  File "calibre_plugins.kobotouch_extended.device.driver", line 211, in _modify_epub
    container = KEPubContainer(infile, common.log, self.clean_markup)
  File "calibre_plugins.kobotouch_extended.container", line 119, in __init__
    self.__run_async_over_content(self.forced_cleanup)
  File "calibre_plugins.kobotouch_extended.container", line 375, in __run_async_over_content
    self.__run_async(func, names)
  File "calibre_plugins.kobotouch_extended.container", line 368, in __run_async
    future.result(timeout=10)
  File "concurrent/futures/_base.py", line 432, in result
  File "concurrent/futures/_base.py", line 388, in __get_result
  File "concurrent/futures/thread.py", line 57, in run
  File "calibre_plugins.kobotouch_extended.container", line 310, in forced_cleanup
    self.flush_cache()
  File "calibre_plugins.kobotouch_extended.container", line 170, in flush_cache
    self.__run_async(self.__flush_cache_impl, args)
  File "calibre_plugins.kobotouch_extended.container", line 368, in __run_async
    future.result(timeout=10)
  File "concurrent/futures/_base.py", line 432, in result
  File "concurrent/futures/_base.py", line 388, in __get_result
  File "concurrent/futures/thread.py", line 57, in run
  File "calibre_plugins.kobotouch_extended.container", line 174, in __flush_cache_impl
    self.commit_item(name, keep_parsed=True)
  File "calibre/ebooks/oeb/polish/container.py", line 1025, in commit_item
  File "calibre/ebooks/oeb/polish/container.py", line 1011, in serialize_item
KeyError: 'OEBPS/Text/Titlepage.xhtml'