Ok, then
(-) make sure the multicast executes on all clients (e. g. via a print node)
(-) make sure that all the values are what you expect them to be (the values you get out of the multicast and also things like “GetActorEyesViewpoint” since some things may not give you the same result on a client vs server since some things like other controllers do not exist on clients)
So basically go step by step via prints/debug and see where the difference is between running it on server and client