Works fine on Dedicated Servers with 5 clients. I’m using it on Steam, in my game No1Lives, right now. And we host 10 Dedicated Servers that each can handle 20 clients.
Leaving this here for the future:
Ryan Laley - “Unreal Engine 4 Tutorial - Online Multiplayer Part 3: Online Doors”
That is not a good way to do this. Multicast is Fire and Forget and if the client is not network relevant he would not get the updates when he becomes relevant.
The best way is to create a RunOnServer function then open the door via timeline and make a timeline to be replicated inside timeline settings. That would always update to every client joining to game late or that becomes relevant if they were too far from the door when it was originally updated.
Edit: You mentioned the timeline. But yes, in that case, do only RunOnServer to save the bandwidth.
The only reason to use Multicast is for the effects that are done only once and you don’t care about them after that.