Device disconnects from Ubuntu when I send ebook via Calibre

[Tarcizio Zanfolin]

The device Kindle 3rd gen. disconnects from Ubuntu when I send ebook via Calibre.
I keep seeing the device in Calibre but the device is off the computer.

I get this error report:

calibre, version 3.21.0
ERROR: Error: Error communicating with device

[Errno 2] No such file or directory: '/media/tarcizio/Kindle/'

Traceback (most recent call last):
  File "/usr/lib/calibre/calibre/gui2/device.py", line 87, in run
    self.result = self.func(*self.args, **self.kwargs)
  File "/usr/lib/calibre/calibre/gui2/device.py", line 591, in _upload_books
    metadata=metadata, end_session=False)
  File "/usr/lib/calibre/calibre/devices/usbms/driver.py", line 306, in upload_books
    path = self._sanity_check(on_card, files)
  File "/usr/lib/calibre/calibre/devices/usbms/device.py", line 937, in _sanity_check
    sanity_check(on_card, files, self.card_prefix(), self.free_space())
  File "/usr/lib/calibre/calibre/devices/usbms/device.py", line 185, in free_space
    stats = os.statvfs(self._main_prefix)
OSError: [Errno 2] No such file or directory: '/media/tarcizio/Kindle/'

[Götz Waschk (goetz-waschk)]

I have the problem with books that have to be converted first, e.g. EPUB. After the conversion, when I reattach the Kindle and press the 'send to device' button again, the book is copied to the Kindle just fine.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[zra7 (zra7)]

Same issue here. Different Kindle models.
Can confirm that this is a calibre on Ubuntu issue.
calibre:3.21.0+dfsg-1build1
Ubuntu:18.04.3 LTS

Verified by testing with:
1. 2 different Ubuntu machines, same USB cables, same set of Kindles - same problem manifests itself
2. A different Arch Linux machine, calibre 4.9.1-1, same USB cables, same set of Kindles - no problem at all.

[Anita (a-lewis)]

Also had problem with Ubuntu 18.04 and version 3.21 calibre. Fixed using upgrade info at calibre which installed calibre 4.15:

sudo -v && wget -nv -O- https://raw.githubusercontent.com/kovidgoyal/calibre/master/setup/linux-installer.py | sudo python -c "import sys; main=lambda:sys.stderr.write('Download failed\n'); exec(sys.stdin.read()); main()"