[vmz]

I noticed that gradually (during months/years) I started to get slow page switches in PDF. First for some files, which was newly published, while old PDFs worked okay. Then I noticed it even for very old PDFs which worked perfectly before. The slowness increased to the point of tens of seconds, and I also started to notice that some pages cane be not displayed at all (they are switching, very slowly, but the screen is blank). Slowness didn't affect mobi books at all. Finally Kindle just got frozen during PDF page switch.

I held power slider for 30 seconds (15 seconds is required in manual) then released it, to do some "reset". Device restarted with some progress bar. Books, collections, highlights and books progress persisted, but books were unsorted as they were never opened before, I guess some timestamps got reset.

More importantly: all PDFs started to work perfectly again, fast page turns even on "new" PDF files (I first thought the problem was because of some "modern" internal PDF markup for recently published files).

I never did such reset during my Kindle use before (I used Kindle for couple of years, before that it was unused for years since the purchase in 2011). It looks like some internal caches were gradually filled with some accumulated data which caused PDFs to become slow. Then these caches were purged on reset and PDFs became fast again. This is my theory but of course I don't know anything about Kindle firmware.

Now I wonder how long PDFs will remain fast, will the reset work again, and what is the actual cause of this.