[Flaviocc]

OK, I will give up.

I DID step by step and did another test:

EPUB to AZW3 - WITHOUT ANY SETTINGS / EXTRA CSS ETC.

Page setup in Calibre - as Jon said: -0.1pt

Calibre give me the AZW3 - and I load this PURE AZW3 without any changes on Kindle. Kindle display to me the book with the default kindle firmware margins. No error. Fwd and bcw pages - NO ERROR.

I deleted this file from Kindle.

Opened the same AZW3 file on Calibre editor - look for any @page setup css (none) - Pasted the JON code ON THE TOP of the CSS, saved and load on Kindle.

The book now has the margins as I set. Fwd a few pages. Leave the book. Open again, fwd a page and ERROR. Closed the book, opened another randomly book, close, open the book 1 again and ERROR.

So, the error appears AFTER the code.

And in the past I used to use the SAME code without any problems.

EDIT.: just to be clear - I have a lot of books that I did the margin settings before, that I had no problem when I read them, I opened a few of these books and I have the error - so it's not a config problem.