Scheduled backup completed with warnings for some domains:
Warning: domain "example.com"
backup_restore_helper utility returned incorrect result. Web settings, composer instances, scheduled tasks and database users have not been dumped. Please, contact your service provider
The backup for some domains completed with above mentioned error message.
This issue is because the hosting type for those domains was set to 'forwarding'.
This is a software issue with internal ID PPP-18396 . It is fixed in Plesk 12.5 MU #10.
Apply the latest Plesk microupdates .