Your definition of xapRights conflicts with the existing xmpRights pre-defined by ExifTool. Since the namespace URI is the same, the tags are equivalent. When reading metadata, your xapRights definition will have no effect, but when writing the effect will be to duplicate tags with both "xmpRights" and "xapRights" namespace prefixes. To fix this, the xapRights definitions should be removed from your config file.