[Koha] error message while doing z39.50 search

While doing z39.50 searches today, I was getting an error message for some books. When I typed the ISBN and hit search, this is what I saw: Koha Error The following fatal error has occurred: Wide character in null operation at /usr/share/per15/MARC/Charset/ Table.pm line 96. I can't seem to find a whole lot about error messages in the manuals. The 2 groups of books that were giving me trouble were Harry Potter books and American Girl books. Any advice? Thanks, Shelley