Visually its not attaching them on the clients. The server shows correctly but not not the clients. One thing I just noticed while testing it is that when running dedicated an a client tries to pickup a container its placing the attached container at what appears to be 0,0,0 location or somewhere there about.
So its making me wander if something is going on with the Attach Actor to Actor event. Its just odd that it will work on the server and single player works fine but multiple clients a no go on them.
It works similar I guess to the space ship and cows. That stores the objects in an array and drops them them. Here I am just attaching an actor to an actor for visual / transport purposes.
With it set to multicast it shows on the client that it happens on but still no other client is picking it up visually. Also on multicast when its dropped you never see it appear on the other clients.
The physics are odd under multicast since the server is handling all the physics in the game it makes the object appear out of place at times on the client that picked it up. (doesnt show anything for the other clients)