game.ReplicatedStorage.ChangeCrate.OnServerEvent:Connect(function(plr,str) local stats = plr:WaitForChild("stats").CrateValue local String = str stats.Value = String end)
Event^^ Apparently str is an Instance.
local plr = game.Players.LocalPlayer event:FireServer(plr,"Large Crate")
What I fired ^^
:FireServer() does not require a player instance as the first argument. However, since you provided it, the "str" variable is actually the player instance. This is because :FireServer() accepts a tuple of arguments,
To fix it, you can do this.