In order to workaround this problem (and re-establish IPv6 connectivity), a downgrade of the quagga package can be done.
For this we add the 'oldstable' entry to sources.list and pin the quagga package to the old version.
Entry to add to /etc/apt/sources.list:
deb http://mirror.switch.ch/ftp/mirror/debian/ oldstable main
Entry to add to /etc/apt/preferences:
Package: quagga Pin: version 0.99.22.* Pin-Priority: 1001
After the entries have been added, run apt-get update followed by apt-get install quagga to downgrade to the old quagga package.