LibreOffice Writer 4.2, Hylafax on Lubuntu 14.04, setup fax printer to remove fax#. When I use a spreadsheet with three fax numbers on it to test the mail merge, only one print job starts. I have the “Create single print jobs for collated output” checked, but it is ignored.
This sounds like it may be bug fdo#56807. Please confirm this bug if it does appear to be the same issue as it is awaiting confirmation from a second party. Thanks. Actually, from reading comment #2 it appears that from LO v4.3.x onwards a new workflow (fax4cups) may be required.
EDIT: Bug is fixed for v4.3+.