Upgrade 2.3.3/2.3.4 OK, Quagga didn't start after first boot

[heper]

2 out of 3 systems i've upgraded failed to start quagga on initial boot. On second boot quagga started fine.
quagga is used to for routing subnet towards other ends of openvpn tunnels.

i did the upgrade remotely and had to go in over ssh, using the tunnel network & manually running

/usr/local/sbin/zebra -d -f /var/etc/quagga/zebra.conf
/usr/local/sbin/ospfd -d -f /var/etc/quagga/ospfd.conf

[heper]

same happened again when moving from 2.3.3 –> 2.3.4