I've seen around 30+ reports of this on Reddit since Feb. 21 2026. Regarding usb loaded/sideloaded AZW3 books I've seen these problems reported:

1) Page numbers don’t work

2) % read tracker doesn’t work, always said Read 100%

3) Painfully slow page turns

4) huge margins on fixed layout manga/comics at the top and bottom of the screen, which the community calls "death margins"

(Another 5.19.2 bug where a "Storage is full" error would constantly appear was apparently fixed rather quickly though. Maybe Amazon prioritized bugs that don't affect sideloaded books?)

And apparently logging out of the Amazon account on the Kindle fixes all the problems. But logging back in the problem returns. And some users reported that making a new Amazon account and logging in with that also fixes the problem.

Not everyone will experience the problem, Amazon can remotely activate features so it's possible the "feature" hasn't been activated for you yet.

Sideloading KFX format books doesn't seem to be affected.

Here are some reddit comments quoting amazon customer service I've seen, take them with a grain of salt since these are just reddit comments:

"I fully understand your frustration. It’s true that reading manga or comics requires a full-screen display to be comfortable. I can confirm that we have received several reports regarding these unusual white margins (sometimes referred to as ‘death margins’ by the community) which appeared specifically with update 5.19.2. I am passing on your specific case to our Kindle development team."

I also read another reddit comment that stated that most of the relevant Amazon team at Lab126 was laid off and the remainder are vibing.