[shamanNS]

Your "dump everything into root level of KOReader home folder" + known limitations of FAT32 file system = no way you can dump 1300 book files ( + later also have that number of ".sdr" folders generated) and expect it to work.

If you insist on having that unreasonable amount of books on your Kindle reader you should at minimum seriously considered at least grouping them into "genre" type of subfolders when sending book to KOReader home folder to have better chances of not running into those aforementioned number of files in single level of file system hierarchy limitations of FAT32.

I'm also doing the "dump every book to root level" ( since I really really hate KOReader's archaic folder-centric approach to reader content presentation) but I don't expect to have more then 100 books on my device at any time as I delete stuff I've read and also I don't need and don't like having all my books all on the reader device (that's what Calibre library is for) to needlessly slow down on-device search and rarely transfer more then 15-20 books in advance.


As for the Calibre metadata search issues those are probably mix of hardware limitations an software issue of parsing that large JSON file using the code library KOReader uses to do that job.