On a remote backup the disk quota was reached and borg failed to connect because borg serve just dies and locally I get:
Connection closed by remote host. Is borg working on the server?

I couldn't find a way to get it working again, so I ended up having to delete the full backup and loose all history.

I found the storage_quota and additional_free_space options, but no way to set them on an existing backup except by manually using sftp. It seems only --storage-quota is exposed via the init command, but not the other option (which from what I read seems more useful).

Locally I have borg 1.1.17, not sure what version Hetzner has on its storage boxes/backup spaces.

Shouldn't additional_free_space be set by default to prevent unrecoverable errors like this?