Projectile attack fully works in studio test mode, however not in play mode?

(My filtering enabled is off)

local tool = script.Parent
local player = tool.Parent.Parent
local mouse = player:GetMouse()
local root = player.Character.HumanoidRootPart


tool.RemoteEvent.OnServerEvent:connect(function(player,mousehit)
    if player.Character:FindFirstChild("multiattackprevention") then return end
    local multiattackprevention = Instance.new("StringValue")
    multiattackprevention.Parent = player.Character
    multiattackprevention.Name = ("multiattackprevention")
    local hitcooldown = false
    local animation = player.Character.Humanoid:LoadAnimation(tool.SuperJump)
    animation:Play()
    local bv = Instance.new("BodyVelocity")
    bv.Parent = player.Character.Torso
    bv.Velocity = Vector3.new(0,250,0)
    wait(1)
    bv.Velocity = Vector3.new(0,0,0)
    wait(0.01)
    bv:Destroy()
    wait(0.4)
    player.Character.Torso.Anchored = true
    root.CFrame = mouse.Origin
    local animation2 = player.Character.Humanoid:LoadAnimation(tool.Cast)
    animation2:Play()
    wait(0.5)
    local magmadrag = Instance.new("Part")
    magmadrag.Transparency = 0.5
    magmadrag.Parent = game.Workspace
    magmadrag.Position = player.Character:FindFirstChild("Right Arm").Position
    magmadrag.CanCollide = false
    magmadrag.TopSurface = ("Smooth")
    magmadrag.BottomSurface = ("Smooth")
    magmadrag.BrickColor = BrickColor.new("Bright red")
    magmadrag.Material = ("Ice")
    magmadrag.Size = Vector3.new(30,30,30)
    local bv = Instance.new("BodyVelocity")
    bv.Parent = magmadrag   
    bv.MaxForce = Vector3.new(1e8,1e8,1e8)  
    bv.Velocity = mouse.Origin.lookVector * 150
    local sound = Instance.new("Sound")
    wait(0.5)
    magmadrag.CanCollide = true
    multiattackprevention:Destroy()
    wait(0.5)
    player.Character.Torso.Anchored = false
    magmadrag.Touched:connect(function(hit)
        magmadrag.Anchored = true
        bv.Velocity = mousehit.lookVector * 0
        if hitcooldown == true then return end
        local enemy = hit.Parent:FindFirstChild("Humanoid")
        if enemy == player.Character.Humanoid then return end
        if enemy then
            enemy.Health = enemy.Health - 400
            hitcooldown = true
            wait(3)
            magmadrag:Destroy()
        else wait(3)
            magmadrag:Destroy()
            wait(0.5)
        end
    end)    
    wait(10)
    magmadrag:Destroy()
end)    

So this script runs perfectly fine in studio test mode, however in play mode, the player jumps up but then simply stays anchored in the air and doesn't fire the projectile.

In play mode server log I get the error:

Players.Citranix.Backpack.Magma Dragon.Script:24: attempt to index upvalue 'mouse' (a nil value)

I do not want the projectile to fire towards the original mouse hit which fired this function, I want it to delay and then shoot towards where the players mouse currently is.