Which is why the Unraid regular container startup has customizable delays between containers.
Black start from nothing is easier, partially running start during backup sequence is more complex, it needs even better customizations. Shutdown and startup conditionals and/or delays would be ideal.
As an example, for my nextcloud stack I'd like nc to be stopped, wait for it to close completely, stop collabora, stop mariadb. Backup all three. Start mariadb, start collabora, wait for those to be ready to accept connections, start nextcloud.
The arr stack is even more complex. The arr's and yt dl need to be stopped, then the nzb, then the torrent and vpn. Startup should be exactly the reverse, with ping conditionals ideal, blind delays acceptable.