[rtoz]

I use Mac OS (Venture 13.1), Calibre 6.11.
My kindles are : 1. Latest Paperwhite (11th Generation), 2. Latest Oasis

I have a very large personal library (over 4K books ) and I transfer them to all my devices.
1. I converted my epub books to AZW3
2. Selected 600 books and clicked 'Send to device'
3. After the transfer was done I've disconnected the kindle
4. The next time I connected the kindle to the calibre - the count of the books on the device displayed 1200. Every book was duplicated with another small file with the same name but with the '.' in front of the name. Now when the whole transfer is completed, I have 9660 books on my device with the 4828 books in my library.

I never had such issues with my old Kindle paperwhites. Also the performance of the transfer is not the best - transferring the last 1000 books out of 4828 took 9.5 hours. The connecting/reading the book list on the device takes at least 5 minutes. I was hoping that maybe there are some settings in calibre I am missing that could improve my experience ?

Thank you