If you see the error "mysqli object is not fully initialized" while running a backup from the CLI or through a CRON job, it means PHP can no longer connect to the database server during the backup. This is a database server configuration issue, not a bug in Akeeba Backup.
The most common causes are:
Low connect_timeout value. Your database server's connect_timeout setting is too low for the number of connections being made during a backup. Increase it in your MySQL or MariaDB configuration.
Low max_connections value. The server may be too slow at disposing of closed connections, causing the connection pool to be exhausted. Increasing max_connections can help.
This issue is particularly common on resource-constrained environments such as NAS devices and lower-end computers running a local MySQL server. Contact your hosting provider or database administrator to review and adjust these settings.