This happens at different points when transferring books from Calibre via Wireless Device Connection. Sometimes it takes 10-30 min, sometimes a few hours, but it ends up happening eventually. This is the error log from Calibre itself:
Spoiler:
calibre, version 5.8.1
ERROR: Error: Error communicating with device
[WinError 10054] An existing connection was forcibly closed by the remote host
Traceback (most recent call last):
File "calibre\gui2\device.py", line 89, in run
File "calibre\gui2\device.py", line 592, in _upload_books
File "calibre\devices\smart_device_app\driver.py", line 50, in _synchronizer
File "calibre\devices\smart_device_app\driver.py", line 1497, in upload_books
File "calibre\devices\smart_device_app\driver.py", line 732, in _put_file
File "calibre\devices\smart_device_app\driver.py", line 614, in _send_byte_string
ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host
I have the "calibre.companion.debug.log" but it is very long and I am unsure what data from it would be helpful in resolving this.