Actors' parenting get scrambled on restart! Bug or 'feature'?

Hi All,

I’m making these Blueprint actors that for them to work correctly depend on how they are parented in the Outliner.
But I am noticing that every other time I open the game in the editor the order of them get scrambled so that the parented is not any longer as I left it last time I save that map.

Is this something that people have noticed?
It it a bug or just the way Unreal operates?
Is there a way to make it work?

Here’s an example on how I need it to be layed out,

But here’s how it looks after a save map then close Unreal and open again,