Ensure that you set all relevant object properties (the Value property) before you set Parent, that way all the properties are properly set up when the object replicates. It could be the case that the LocalScript replicates before the property changes do, and it runs without having the proper values. Wouldn’t know unless we saw the server code, though.
Side note: an ObjectValue is probably better than a StringValue when referring to a Player object.
Cloning LocalScripts isn’t the best way to go about creating effects locally. Perhaps you should make a RemoteEvent and listen to OnClientEvent via a LocalScript, then perform the effect when the event fires.