Book changes formatting in the middle

[pepak]

I have a strange problem with my PRS-505: I scanned a book, then OCRed it and saved the text as HTML. Then I cleaned the HTML and checked it in the browser and validator to make sure no forgotten B or H# tags remain. Everything seemed fine at this point.

Then I converted the book to LRF using Calibre's any2lrf with the following params:

@echo off
setlocal
set book=book.htm
set title=Book
set author=Book Author
set authorsort=Author Book
set chaptertags=h[23]

set metadata=-t "%title%" -a "%author%" --author-sort="%authorsort%" --header --cover=small.jpg 
set chapters=--chapter-regex=^ --force-page-break-before-tag=%chaptertags%
d:\progs\libprs500\any2lrf.exe %metadata% %chapters% "%book%"

I checked the resultwith lrfviewer and once again it seemed fine. When I loaded the book into my reader, I was a bit surprised that the paragraph font is a lot smaller than usual, but I just zoomed to Middle and continued reading. Until I reached chapter 6, where suddenly two things happened:

1) The chapter title had a page break before AND after it, while all other chapters onle have a page-break-before.

2) The paragraph font became much larger than before.

I can't understand what's up with it. The source HTML uses exactly the same structure with chapter 6 as it does with chapter 5, and after converting the LRF to LRS, I don't see anything different in that format either. Which is pretty much confirmed by lrfviewer which - in this one instance - shows different output than the real viewer.

Does anyone have any idea what could be the problem? I am pretty sure it's not a layout thing, as I even deleted the cache.xml file and let the Reader rebuild it.

[pepak]

Update: Just got to chapter 7 and it is in the same format as chapter 5 (and earlier).