Okay, I have had a look at the project @BrainDeadLabz and I have a theory as to what the problem actually is, I could be wrong but it’s worth investigating. None of your actors are replicating so nothing is sending messages or getting overridden by the server. This is illustrated by the fact that when you look at the world outliner on the server when the client rotates their preview character none of the preview characters’ rotation change on the server.
However, you do use a render target to capture that preview character and display it in your UI. I theorise that because you have the 1 render target, 1 material and testing on 1 machine what is actually happening is that when you spawn in the client’s preview character that ends up overriding the data the server was passing in and just displays the client’s preview character. One odd thing to note about this is that it is only 1 way? The client will always take priority even if the server’s inventory is displayed last.
I’m not too familiar with render targets, I haven’t messed around with them before but I think this is worth investigating. Check out a reference here: Rendertargets and multiplayer..?