Have an issue with indexing

[greylogan]

I have the new 2018 Paperwhite (10th Gen) and I have books that I got from other places and converted with Calibre to AZW3. When I send them over to the Kindle, everything is fine. When I restart my Kindle, the same books I send over begin indexing again. And it happens again and again as I restart my Kindle. I restart because I want to know if this issue is persisting. It doesn't happen all the time, and the books I am sending over are fine and free of issue. I don't know if this is a new feature with Kindle's to make sure you buy just from Amazon and nowhere else or else the books won't index properly or if my brand new Kindle is already defective for some reason or another issue entirely. does anyone else have this issue?