MonetDB, data loss in restart server

Hello,

I have used the MonetDB in production for some time, and I have nothing to complain about, are tables with more than 30 columns and 30 million records, do analysis through cubes in Pentaho / Saiku. Have restarted the server several times, and never had problems with loss of data.But today, after performing a query that was consuming a lot of machine, stopped the database, and when I started, data from some columns were blank. How can it, will the data were still uncommitted? when performing a query the MonetDB changes the data or reorganized? which may have occurred, I am concerned.