This happend on Proxmox KVM host server when tried to restore Snapshot of an Virtual machine (VM).

bridge 'vmbr*' does not exist
/var/lib/qemu-server/pve-bridge: could not launch network script
Failed: exit code 1

(i had vmbr1)


cat /etc/network/interfaces

auto lo
iface lo inet loopback

auto vmbr0
iface vmbr0 inet static
bridge_ports eth0
bridge_stp off
bridge_fd 0
bridge_maxwait 0

auto eth0
iface eth0 inet manual

Im not sure how to fix it, but maybe try to copy whole vmbr0 section and paste it below as vmbr* or any other which is demanded. And maybe try to tweak IP values of thet newly pastet section. (ip calculator). And maybe try tremoving "bridge" lines from that pasted section.
May try service networking restart on host node.