How to edit raw data in contacts

Hello,
some of the ics-files of addresses in my addressbook are getting bigger and bigger without any intervention of me. Looking into the raw data I see doubled urn:uuid-entries like this:

BEGIN:VCARD
VERSION:4.0
PRODID:-//MailClient.VObject/9.2.2258.0
UID:urn:uuid:urn:uuid:urn:uuid:urn:uuid:urn:uuid:urn:uuid:urn:uuid:urn:uuid
:urn:uuid:urn:uuid:urn:uuid:urn:uuid:5a82afef-c1f1-4288-ab99-9a428506535b
FN:Thomas T…

END:VCARD
I do not know how this happens and which program does it. As I know the urn or uuid is used by a database I don’t want to delete it. I am looking for a way to delete most of the uuid:urn… entries (exept for one) by editing the ics file.
I’m looking for suggestions to edit vcards without destroying the connection to the related data base. Thanks in advance. Thomas