I don't think there's an error. It's just that this latest version of Knoppix pushes the size limit more than the other versions you tried to remaster. Therefore, unless you take care to get maximum compression, the iso won't fit.

You may find the easiest things to delete are some of the language files for KDE. They are big, plentiful and mostly not needed for anything specific enough to require remastering. Deleting one or two you won't be using should do the trick.