In contrary to version 2.6.0, the current head version von docx4j.ContentControlBindingExtensions generates an invoice_bound.xml which is not accepted by my version of word 2010 (unknown error at /word/document.xml , line 98, row 0).
This is obviously due to the fact that empty <sdtContent/> elements are not accepted in w:tr/w:sdt: Changing them for <w:sdtContent><w:tc><w:p/></w:tc></w:sdtContent>, the document is working perfectly (interesting enough, changing the first column suffices to "repair" the document, word then omits the second row of the table).
However, compared to the result of the 2.6.0 version processor, still the information regarding the preferred table cell width is lost, so an easy fix by adding another special case to bind.xslt seems to be unreasonable. For the moment, I'd consider binding of sdt cells in trunk as broken.