There is a funky thing that happens at the end of chapters occasionally in ePubs, it appears to be caused by the following piece of CSS that Kobo include in the device's built-in ePub stylesheet (%1 is a variable that refers to the line height selected by the line spacing slider):
Code:
body { padding-bottom: %1em !important; }
If you set orphans:1;widows:1; in the book's stylesheet (and make sure to remove the publisher's orphans and widows settings if they have set them) then that seems to reduce the frequence of the problem, but it still occurs occasionally.
There is a patch named `ePub disable built-in body padding-bottom` that, combined with setting orphans:1;widows:1;, fixes the problem completely (in my experience.)
As far as full-screen mode goes, there are some problems with full-screen mode when reading KePubs (and patches to fix most of them), but I've read hundreds of ePubs in full-screen mode and never come across a single problem ever.
Edit: I think there is a way to test whether the above is the cause of your problem by editing the book, without the need to patch (this relies on the Adobe ePub reader's unusual interpretation of !important that allows the publisher to override !important in the device stylesheet by subclassing in the book's stylesheet.)
In the book's stylesheet, add the following class:
Code:
.do-not-pad-my-bottom { padding-bottom: 0; }
then in the html files, change <body> to <body class="do-not-pad-my-bottom">
Edit2: If you convert the book to ePub with Calibre then you might be able to fix this problem automatically during conversion by adding
body { padding-bottom: 0; } to the conversion settings in Look & Feel > Styling > Extra CSS.
Calibre automatically creates a .calibre subclass for body and adds all the styles that were applied directly to body in the original book to body.calibre in the converted book. Normally this causes nothing but problems, because it means the device's adjustment sliders can no longer override the body styles in the converted book, but for this particular problem it might be just what is needed.
Edit3: And finally I should add: the reason the padding-bottom problem seems to occur randomly is that it is triggered only when the last line of text in a chapter would fall on the last line of the page -- or if widows/orphans is set higher than 1, then maybe also when the last page of the chapter has only one line of a multi-line paragraph. That would also explain why switching from full-screen to normal reading mode, or changing the margins, etc., appear to make the problem go away (but actually just make it pop up somewhere else), because those adjustments change the position of the last available line on the page.