Keep in mind that while you may initially start your backups at a time ie each day at 9am, but then as you add more websites to your cluster as well as other factors, such as the number of concurrent backups you choose, even network speed etc may also cause your back timing to creep. Enhance backups are very smart as they are not designed to run at the same time each day, but rather to hit the targets you set (minimum backup age, maximum backup age etc)
For us, we are not so worried about when our backups run, just that they stick to the minimum and maximum backup age. We don't see any loads on our backup server when backups run now. All our backups hit their targets, but the times they run are not the same each day..that should, in my opinion, not be something you give any thought to (the time they run). Ideally, I'd prefer to see backups running all through the day (random times) with no particular noticeable impact on our cluster.
(Yes, there is the time you can set in Enhance to only allow backups in that window. I don't recommend or suggest this be something you worry about in a production cluster. Loads and traffic vary for many reasons, and you will actually increase loads/traffic if you force your backups to only run during a particular time window. If you think you need to do this, perhaps you don't have enough capacity on your network/cluster)
To sum up:
Backups running at random times is not a failure or a bug, and it doesn't need to be fixed. It's a very clever feature in Enhance. Even if you do try to "fix" it, you'll just be back (probably when you have a decent number of websites) to "random times" eventually anyway.
