Drauku • 5 yr. ago • Edited 5 yr. ago
EDIT: I think I found a solution to this. When I was converting the book files to .mobi format, Calibre automatically added a '[PDOC]' tag, and this makes the Kindle organize those "doc" files differently (as personal documents). As soon as I removed that tag from the conversion process, no more lost books! I had to go back through my entire Calibre library and re-convert the .mobi files in order to remove the tag. If this still doesn't work, try adding the '[EBOK]' tag to the MOBI output convert dialogue.

Here's a good guide on how to remove the [PDOC] tag in Calibre: https://www.tech-recipes.com/rx/20147/kindle-fire-how-to-display-mobi-files-as-books-and-not-documents/

The above guide describes how to remove the tag on each conversion, if you want to remove the default behavior of adding [PDOC] every time you convert to .mobi, you need to remove the tag from the Convert settings for the .mobi format