Hi,
The logs shows that the backup process is timed out or killed off.
Could you try to reduce the backup archive split size. This will split the backup into smaller, more manageable files.
To do this, open the ‘expert settings’ section of the UpdraftPlus Settings tab, and find the ‘split backups every’ option. Set this to 100Mb or lower value, save your settings and run a new backup.
If the issue persists, please ask your hosts/server admin to investigate their PHP error logs. These logs should contain more information on the exact issue that is causing the backup process to halt.
Regards,
Bryle