Reference to child actor across RPC's not working

Hi all, I wonder if anyone can point me in the right direction on a RPC issue I’m having.

I have an object that is static in the persistent level that is loaded by the listen server. It has several “button” objects that are child actors. Each one of them has an event dispatcher that various BP’s bind events to dynamically.
I want to have the client respond to the push of the button by telling the server it was pushed, then having the server issue a multicast event to all the clients to call the event dispatcher.
However, if I put the child actor simply as a reference to an actor into the rpc - receiving server script throws and error:
Warning: UPackageMapClient::InternalLoadObject: Unable to resolve default guid from client: PathName: ChildActor_GEN_VARIABLE_UIDynamicElementButton_BP_C_CAT_830,

How do I correctly pass a ref to this object?