Adding page breaks in Calibre breaks ePubcheck validation
I have an ePub which I have exported from InDesign (without page breaks).
This ePub passes the ePubcheck validation (except for the date, which is fixed if I run Calibre's epub-fix commandline tool).
Next, I add page breaks in calibre by converting from ePub to ePub, and adding page breaks before chapter openings.
This works fine, and I'm able to view the ePub with the correct page breaks in ADE and calibre's viewer.
However, the ePub no longer passes the ePubcheck validation. Each page break (there are 150 of them) produces this error:
Error: test.epub/OEBPS/Test_split_125 [any number between 1 and 150].xhtml<16>: element "a" from namespace "http://www.w3.org/1999/xhtml" not allowed in this context
running calibre's epub-fix does not help in this case.
If anyone has an idea what's wrong and what I can do to fix this, that would be very kind.