My MBLD backup was working ok until Ii did the following steps.
I created in a directory a new sub directory and moved all the existing subdir to the new created one.
I guess that there is somewhere a flag which stated that the existing subdirs an its content are already been backed up.
New created files in the subdirs are being baced up correctly.
Well the circumvention was to move the subdirectory to another directory on which the backup was disabled. Ran a backup, moved the subdirectory back to its original place, ran a backup and it was now succesfull.