Symantec support could identify the problem. The error message is caused by special characters (like "~", ")", "[", ...) in filenames while iterating through the file system. I have seen hundreds of files with such characters on customers unix server, so making an exception for such a huge amount of filenames is not feasable.
Nevertheless, now that I know the reason for the error, I reviewed all the filenames causing the error. These files aren't from higher interesst as they are no configuration files. It is ok to ignore the error message for these files.