[Koha] EAN13-label printout incorrect

Hello Koha-Mailinglist, related to a rejected bug-report I found out, that the KOHA-printout of EAN13-lables may be incorrect. My professional-grade USB-barcodereader (Manhattan 177665) is reproducibly reading only 12 digits instead of 13 digits. On some reason the first digit is missing. I've checked it many times also with a plain text-document where the numbers are typed in as if they are coming from a keyboard. Standard ISBN-book-labes (EAN13) are read correctly with all 13 digits. Did anybody came acrosse the same or a similar problem, or is able to reproduce it? Please also refer to my KOHA-printout of EAN13-lables in the attachment. (Sorry now with attachment...) Best Regards Kamilla Braun