Hi Micha,
Not worked to you the option error log on import from command?
http://help.sap.com/hana/html/sql_import_from.html
How to load files into HANA
http://scn.sap.com/thread/2072330
If I remind well the non processed lines are saved on this error log file and the good ones saved.
In this case you have on this err file what you are trying to catch on exception.
Regards, Fernando Da Rós