LibreOffice 5 for OS X mail merge problem

I cannot successfully use mail merge with a writer doc and an odb. At the salutation dialog, no matter what I choose, when I click next I get:

LibreOffice 5 fatal error sfxbasemodel::impl_store (filename) failed 0x81a

I cannot find any solution on google for this. What is causing the error, and what is the solution please?

I get exactly the same error at the same step of merging assistant.
I have a writer document (odt) and use a JDBC connector to mysql from where I can have the table and the list of fields.
(filename) is a sxw file in /tmp
In libreoffice 4.4.7.2 in Mageia 5

Just tried with 5.0.4 from Libreoffice site, and I get a crash at the same step.