Kindle overwriting custom covers for books with ASINs

[glowby]

I have specifically chosen covers for all of my books in my Calibre library. All my books are in the .AZW3 format. I have also used the "Quality Check" plugin to fix ASIN to all of my books, so that Goodreads integration works. However, sideloading the books into my Kindle (via "send to device" in Calibre) results in the covers of my books being overwritten by the Kindle, and it seems to be pulling covers from the Amazon server.

I have searched through many posts about this issue, and it seems to be known that the Kindle will always overwrite the cover set in Calibre to one from its own servers, if an ASIN is set.

I have found that when my Kindle is plugged in, and browsing to \System\thumbnails gives me all the thumbnails that the Kindle has forced downloaded over my own custom covers, in the format of: thumbnail_[ASIN]_EBOK_portrait.jpg

Saving my custom cover in that format (and changing the [ASIN] to the corresponding ASIN of the book's title), and rewriting the file in the thumbnail folder, and then ejecting my kindle seems to have worked, with my custom cover showing without being overwritten, and Goodreads Integration working fine with my books with ASINs.

The problem is that I have over 300 books in my library, and manually doing this process is unthinkable. Has anyone come up with a better workflow for this, or is there a way Calibre can save the book covers in that thumbnail format?

[glowby]

I have solved my problem! Here are the steps in case anyone else in the future has the same issue,

1. Convert book to .AZW3, I deleted all other formats
2. Fetch Metadata, ensuring Amazon IDs are downloaded.
3. Set your preferred cover
4. Using plugin "Quality Check" > Fix > Fix ASIN for Kindle Fire
5. Plug Kindle in, browse to /system/thumbnails and delete everything in the folder
5. Send all books to device
6. Refresh /system/thumbnails, and you should see the correct number of thumbnails that correspond to the number of books you just sent to your device, in the format of thumbnail_[ASIN]_EBOK_portrait.jpg. Copy all these covers in a different location.
7. Unplug Kindle, and wait about 5 minutes (depending on how many books you have) for Kindle to finish indexing/refreshing all the books. You should see some of your book covers being changed to whatever is being pulled from the Amazon server.
8. Plug Kindle back into computer, browse to /system/thumbnails, delete everything in the folder again
9. Paste all those thumbnails you saved in step 6 back in the /system/thumbnails folder
10. Unplug Kindle, and viola! Your covers should not have changed, and Goodreads integration is working. Your Kindle should just redownload your dictionary covers.

For future books that you add to your device, or if you had to fix metadata of an existing book, follow the same steps, except instead of copying the entire thumbnails files, just copy, delete and rewrite the thumbnail_[ASIN]_EBOK_portrait.jpg file of the book. The ASIN will be in the ID field in metadata as amazon:XXXXXXX.

Credits to this thread from 3 years ago that was the only thread I found that explored this issue in depth!

[ownedbycats]

I just want to say thank you for including the instructions for how you fixed it.