It doesn't do this for me. I've got side-loaded and Amazon store books on the same device, no problem.

It also deleted all my side-loaded books. That was the last straw for me. I only buy DRM-free media from now on and only use respectful hardware. I use my Remarkable 2 primarily for e-reading now, though I concede fully it's not the best user experience for reading. But I don't have to worry that it will delete my books! I can also now "write in the margins" which I've found to be a powerful way to take notes. I can't bring myself to write on physical books, but with Remarkable you can have a copy that is stock and a copy with your notes on it. Best of both worlds!

Huh. All my books are side-loaded and I've not had any issues.

As far as I can tell, it's a fairly rare bug. I've only had it happen to me once in 6 years. But the moment it happened, I decided I was never buying a Kindle again. I still have my paperwhite because it works fine, but it's never connecting to the internet again.

That is strange. I have had a Kindle for years (probably around a decade), upgrading mutliple times. I am using a Paperwhite Signature for the past year or so and I have not experienced this with any books. I have probably 70% Amazon purchased books, but that still leaves a decent amount of side-loaded books (mostly epub).

The only annoying thing I experience is that the cover art will unload on the side-loaded books where you just get the generic cover with the text of the book. But once you click the book it loads the artwork, which seems to last a few days before quickly going back to the generic cover. But the book itself never leaves the device. I can't say I have experienced this ever (except for once, mentioned below) and I have over 150 books on my 32Gb device.

Just some random thoughts I am wondering:

- Is it an ads-supported model (mine isn't)

- Are the books in a broken-DRM .mobi? Not judging, i've done it too, just curious if Amazon has some sort of "signature" in mobis that allow it to detect a book that had DRM removed?

- Are they standard .epub?

- What is the size of the device? (Maybe smaller 8Gb devices will clean up and prioritize non-Kindle content to make way for "official content)

- Which device is it? (Scribe, Oasis, Paperwhite, older paperwhite, etc)

The one time I had it deleting my book was a large book (it was 400Mb) and it was on an older 8Gb paperwhite. I still had PLENTY of storage space available (I was using around 4Gb) but it kept deleting that book. This was the only time I have seen it happen and it was with this one specific book. That was many years ago and I haven't seen it since. That book was a DRM-removed book I got through "shared" means. Which has led me to question if the Kindle removes it because it could detect that the DRM had been removed or because of its large size. But this was a one-off experience for me. The book was readable by the device. It would download for several weeks at a time before being removed. You could redownload it and it would work for weeks again before dissapearing. I never could figure it out.

For me, they were drm free ebooks I bought legitimately and had to sideload via calibre because the kindle doesn't support epub. It's an old Paperwhite, and it only happens when I go out of airplane mode. However, I have to go out of airplane mode (or had to before I ditched the kindle for a kobo) to get library books and the occasional actual Amazon kindle book when I didn't feel like waiting for the library to get me to the front of the list.

*Edit to add: I believe the kindle won't delete epubs you sideload via the Amazon kindle email gateway, but I have no interest in doing that.

I have been using Send to kindle[1] for years to upload epubs directly to Kindle. It even syncs the position in the books so that if I read it on my Kindle, it syncs the position to the Kindle app on my phone.

[1] https://www.amazon.com/sendtokindle

I've found that Send to Kindle does a much worse job at converting to MOBI than Calibre, which is a bit ironic but on par with Amazon's overall treatment of non-Kindle books.

Back when MOBI was still the primary format for Kindles, it would actually allow you to upload .mobi files directly via Send to Kindle.

These days it wants ePub only, but things also seem to "just work", and I always assumed it's because they added support for it on device side. What are the issues that you ran into?

Interesting thread. I wonder if this has anything to do with what I experienced with the one (two, actually) I set up for my mom years back. The books were visible on the filesystem but nowhere to be found when using the device.

Fortunately, getting two units in a row with jarring pink blotches was enough of a non-starter to suggest that she just revert to a V4 without my having to explain the confusing behavior.

I don't have that problem with my paperwhite...

I've side-loaded .mobi and .pdf files, and have never had anything disappear, whilst still buying some things from Amazon kindle store...

Happens to me consistently if my device is on Airplane mode for a long time.

Happened to me also. I will use the device in airplane mode as long as it lasts, but this is my last Kindle.

That’s not right, I always buy books from Amazon over WiFi but also sync my books from Calibre. No issues for probably 10 years.

is your wifi on when you add your calibre books? if so, thats why.

My wifi is alwasy on, I'm using a cable to sync from Calibre though after they kinda deprecated the "E-Mail to Kindle" feature.