[j.p.s]

Originally Posted by jhowell

As a test on my PW3 I changed version.txt to indicate the build of the initial release firmware version (5.6.1.1 build 2634130033) that predates KFX format. After rebooting I downloaded a book that had previously been on the Kindle in KFX format and it downloaded in KF8 format instead.

Thanks.

Does the book have images? If so, were they in an azw6 file, or was everything in the azw3?

Unfortunately the user interface of the Kindle became seriously messed up and unusable, with a mix of old and new UI elements. The top drop down menu could not be activated. Library view disappeared. After opening a book it was impossible to close it through the UI.

That's too bad. I hope it didn't leave any lasting problems.

I can see why they would use version number to select download type and why it would be attractive to use to block downgrades. But it seems it would be a prime generator of new bugs and strange side effects to have it affect UI. I wonder how many lines they have to tweak every time the version changes solely because of this.

I finally restored the version number and did a factory reset to make it usable again.

Update: It appears that during my testing the Kindle "updated" itself to version 5.13.7 which was an older version than was actually running on the device. That may have been the actual cause of the UI failure. I recommend that anyone setting a fake build version should block OTA updates first.

Yes, I think that's pretty much a requitrement for this kind of research.

Thanks for being a pioneer and risking the arrows.