I found that the script creates a /etc/network/interfaces file entry for eth1 along with eth0.
As there is no eth1 (unless you create it) in order to keep it from disconnecting after a while you should delete the eth1 section in that interfaces file.
Unless you remove it you will not be able to restart the service manually as it will error out.
https://tteck.github.io/Proxmox/#iventoy-lxc
The script is under the servers option.