The substitution of the BREAK_HERE string by <br/> when it occurs in a html-table-entry (<td>...BREAK_HERE...</td>) does not function properly. The BREAK_HERE string remains in the PDF.
When the BREAK_HERE string appears in other HTML context, it is properly substituted.
Is this a known undocumented feature.
Can someone give me some tricks to get the proper result?

Are you using JavaScript? Is JavaScript enabled? Are there any errors in the output log?