Sword animation does not play properly in r15 humanoid, why?

So this is the problem, I had this sword been working with r6 without having any problem but now I wanted to turn it to r15, everithing is working exept for one thing. The animation. I have already switched the animations id to r15 animation but for some reason the right arm of the player freezes, like the whole animation plays exept for the right arm of your chacter... Does it have anithing to do with the animation script below? If so, whats wrong? If its not because of the script what do you guys suggest?

local Tool = script.Parent;

local walking = 0
local hold
local walk

enabled = true
function onButton1Down(mouse)
    if not enabled then
        return
    end

    local vCharacter = Tool.Parent
    local hum = vCharacter:findFirstChild("Humanoid")
    hum:LoadAnimation(script.Parent.Slash):Play()
    enabled = false
    mouse.Icon = "http://www.roblox.com/asset/?id=248193486"

    wait(1)
    mouse.Icon = "http://www.roblox.com/asset/?id=248193464"
    enabled = true

end

function onKeyDown(key)
    if walk and (key == "w") or (key == "a") or (key == "s") or (key == "d") then
        walk:Play()
        walking = walking + 1
    end
end

function onKeyUp(key)
    if walk and (key == "w") or (key == "a") or (key == "s") or (key == "d") then
        walking = walking - 1
        if walking == 0 then
            walk:Stop(0)
        end
    end
end

function onEquippedLocal(mouse)

    if mouse == nil then
        print("Mouse not found")
        return 
    end

    local vCharacter = Tool.Parent
    local humanoid = vCharacter.Humanoid

    hold = humanoid:LoadAnimation(Tool.HoldSword)
    walk = humanoid:LoadAnimation(Tool.WalkSword)

    hold:Play()

    mouse.Icon = "rbxasset://textures\\GunCursor.png"
    mouse.Button1Down:connect(function() onButton1Down(mouse) end)
    mouse.KeyDown:connect(onKeyDown)
    mouse.KeyUp:connect(onKeyUp)
end

function onUnequippedLocal()
    hold:Stop()
    walk:Stop()

    hold = nil
    walk = nil
end

Tool.Equipped:connect(onEquippedLocal)
Tool.Unequipped:connect(onUnequippedLocal)