I started to get following errors in logs.
Nov 07 12:04:43 backup pve-firewall[21623]: status update error: iptables_restore_cmdlist: Try `iptables-restore -h' or 'iptables-restore --help' for more information.
Nov 07 12:04:43 backup pve-firewall[21623]: status update error: iptables_restore_cmdlist: Try `iptables-restore -h' or 'iptables-restore --help' for more information.