keys for federal layer has to be defined as string not integer in yaml as topicid could also be a string and is replaced as such in pdf_classes around line 697:
ch_legend_layers:
    '103': ch.bazl.projektierungszonen-flughafenanlagen.oereb
    '108': ch.bazl.sicherheitszonenplan.oereb
    '119': ch.bav.kataster-belasteter-standorte-oev.oereb