Kindle paperwhite [Errno 13] Permission denied : sending metadata to device

Hello,

In the last few days I always got the following error message when I try to send books to my kindle paprewhite either with the reading list or manually with the calibre send to device option.

I tried resetting the calibre and the device as well to factory reset no solution.

I usually send a big batch at the time because I read fanfics which are updated regularly.

Sometime if I send just a few it works but not always, anybody has some idea what could help? I'd appreciate any help. And please write it very throrougly every step I'm not very good with calibrating things. Thx in advance!
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[Errno 13] Permission denied: u'L:\\documents\\my book name here.mobi'

Traceback (most recent call last):

File "site-packages\calibre\gui2\device.py", line 88, in run

File "site-packages\calibre\gui2\device.py", line 592, in _upload_books

File "site-packages\calibre\devices\usbms\driver.py", line 317, in upload_books

File "site-packages\calibre\devices\usbms\cli.py", line 52, in put_file

File "site-packages\calibre\utils\filenames.py", line 190, in case_preserving_open_file

File "site-packages\calibre\startup.py", line 116, in local_open

IOError: [Errno 13] Permission denied: u'L:\\documents\\my book name here.mobi'