issue with last opened position

[cramoisi]

hello,
I got some ebooks that got a correct TOC, are validated with calibre and epubvalidator but they can't register the last opened position. Thus each time i open them up, I'm getting rolled back on page 1. This happen on all my reader and on koreader and nickel so i suspect it's something inside the epub but got no idea where to search... Also, in these books some of the bookmark I created also send me back on page 1.

any help ?