I think I have a similar Problem. I am very confused, does that means Child actors are not “replicated” when you add them to the Pawn directly and not at runtime?
What’s the reason for this? Is it a bug or a feature? 
I thought before about the way to spawn the child actor at runtime and then replicate it. But then I thought its much better to do attach the child directly so the spawned pawns already have the Child Actors attached. In “Editore Gameview” and in “New Window” everything works fine with this solution as intended. No problems, actions in the child actors are replicated fine.
But switching to “stand alone” game shows me, that the child actors on clients are not working. Multicast on server child actor does nothing on clients child actors. I activated replication of course in the BP which is taken as child actor. Also in the “parent” pawn bp I activated everything I found to activate replication for the child, but it is not working.
Why it is working for Actor Components and not for Child actors? Or do I miss something.
If this is not possible and I have to spawn and replicate at runtime I would prefer to go with actor components. Is there any possibility to convert from actor to actor component (of course everything, but not “viewport related”, because actor component does not have this)
My settings in parent to show I tried to set everything to “replicate” on the child what I found:
