The error was the order of the fo:table-footer tag! The fo:table-header and
fo:table-footer tags have to be in the source file before the fo:table-body tag
appears!

I do not know whether that's a FOP compliance or a W3C recommendation.

According to
 http://www.w3.org/TR/xsl/slice6.html#fo_table
the content model of fo:table is
 (table-column*,table-header?,table-footer?,table-body+)

Well, I already told you that FOP occasionally ignores content
in invalid FO documents without telling the user about the
problem. A more common error is forgetting the table-body
tags (http://xml.apache.org/fop/faq.html#table-missing).
Validating against the DTD or XSD which can be downloaded from
the FOP site might help a bit.