In ubuntu_install.sh on line 731, VPNARRAY is loaded with the interface names and it expects them to be distinct without mentioning modification previously.
VPNARRAY=$(grep dev openvpn/*.conf|awk '{print $NF}'|tr '\n' ' '|sed 's/.$//g')
Output of these commands on configs without unique dev tun is: tun tun tun tun tun tun tun tun tun tun tun tun tun tun...