Why does this make my player do weird things?

So, my brother sent me a gun, with a problem. It causes the player to do weird things when it's equipped. Well, it's not my scripting, so I looked at it, and don't understand what is being done exactly. So, I'm here to ask for help. The various things that happen are: The player is flung, prevented from moving for several seconds, or glitched through the floor.

OnEquipped Function

function OnEquipped(M_Icon)
    wait(math.random(10, 40) / 100)
    if Humanoid.Health ~= 0 and (not Selected) and Gun.Parent == Character then
        Selected = true

        BreakReload = false

        --------------------[ FAILSAFE RESETING ]-------------------------------------

        for _, GM in pairs(Ignore_Model:GetChildren()) do
            if GM.Name == "Gun_Ignore_"..Player.Name then
                GM:Destroy()
            end
        end

        for _,c in pairs(Connections) do
            c:disconnect()
        end

        Connections = {}

        --------------------[ CREATING IGNORE MODELS ]--------------------------------

        Gun_Ignore = Instance.new("Model")
        Gun_Ignore.Name = "Gun_Ignore_"..Player.Name
        Gun_Ignore.Parent = Ignore_Model

        --------------------[ MODIFYING THE PLAYER ]----------------------------------

        M_Icon.Icon = "rbxasset://textures\\Blank.png"

        Gui_Clone = Main_Gui:Clone()
        Gui_Clone.Parent = Player.PlayerGui

        SetUpGui()

        Shoulders.Right.Part1 = nil
        Shoulders.Left.Part1 = nil

        PrevNeckCF.C0 = Neck.C0
        PrevNeckCF.C1 = Neck.C1

        BG = Instance.new("BodyGyro", HRP)
        BG.maxTorque = VEC3(HUGE, HUGE, HUGE)
        BG.Name = "BG"
        BG.P = 1e5
        BG.cframe = CF(Torso.CFrame.p, Torso.CFrame.p + Torso.CFrame.lookVector)

        local PlayerFolder = Instance.new("Model")
        PlayerFolder.Name = "PlayerFolder"
        PlayerFolder.Parent = Gun_Ignore

        local AnimBase = Instance.new("Part")
        AnimBase.Transparency = 1
        AnimBase.Name = "AnimBase"
        AnimBase.CanCollide = false
        AnimBase.FormFactor = Enum.FormFactor.Custom
        AnimBase.Size = VEC3(0.2, 0.2, 0.2)
        AnimBase.BottomSurface = Enum.SurfaceType.Smooth
        AnimBase.TopSurface = Enum.SurfaceType.Smooth
        AnimBase.Parent = PlayerFolder

        AnimWeld = Instance.new("Weld")
        AnimWeld.Part0 = AnimBase
        AnimWeld.Part1 = Head
        AnimWeld.C0 = CF(0, 1, 0)
        AnimWeld.Parent = AnimBase

        local ArmBase = Instance.new("Part")
        ArmBase.Transparency = 1
        ArmBase.Name = "ArmBase"
        ArmBase.CanCollide = false
        ArmBase.FormFactor = Enum.FormFactor.Custom
        ArmBase.Size = VEC3(0.2, 0.2, 0.2)
        ArmBase.BottomSurface = Enum.SurfaceType.Smooth
        ArmBase.TopSurface = Enum.SurfaceType.Smooth
        ArmBase.Parent = PlayerFolder

        ABWeld = Instance.new("Weld")
        ABWeld.Part0 = ArmBase
        ABWeld.Part1 = AnimBase
        ABWeld.Parent = ArmBase

        local LArmBase = Instance.new("Part")
        LArmBase.Transparency = 1
        LArmBase.Name = "LArmBase"
        LArmBase.CanCollide = false
        LArmBase.FormFactor = Enum.FormFactor.Custom
        LArmBase.Size = VEC3(0.2, 0.2, 0.2)
        LArmBase.BottomSurface = Enum.SurfaceType.Smooth
        LArmBase.TopSurface = Enum.SurfaceType.Smooth
        LArmBase.Parent = PlayerFolder

        local RArmBase = Instance.new("Part")
        RArmBase.Transparency = 1
        RArmBase.Name = "RArmBase"
        RArmBase.CanCollide = false
        RArmBase.FormFactor = Enum.FormFactor.Custom
        RArmBase.Size = VEC3(0.2, 0.2, 0.2)
        RArmBase.BottomSurface = Enum.SurfaceType.Smooth
        RArmBase.TopSurface = Enum.SurfaceType.Smooth
        RArmBase.Parent = PlayerFolder

        LWeld = Instance.new("Weld")
        LWeld.Name = "LWeld"
        LWeld.Part0 = ArmBase
        LWeld.Part1 = LArmBase
        LWeld.C0 = ArmC0[1]
        LWeld.C1 = S.ArmC1_UnAimed.Left
        LWeld.Parent = ArmBase

        RWeld = Instance.new("Weld")
        RWeld.Name = "RWeld"
        RWeld.Part0 = ArmBase
        RWeld.Part1 = RArmBase
        RWeld.C0 = ArmC0[2]
        RWeld.C1 = S.ArmC1_UnAimed.Right
        RWeld.Parent = ArmBase

        LWeld2 = Instance.new("Weld")
        LWeld2.Name = "LWeld"
        LWeld2.Part0 = LArmBase
        LWeld2.Part1 = LArm
        LWeld2.Parent = LArmBase

        RWeld2 = Instance.new("Weld")
        RWeld2.Name = "RWeld"
        RWeld2.Part0 = RArmBase
        RWeld2.Part1 = RArm
        RWeld2.Parent = RArmBase

        if S.PlayerArms then
            FakeLArm = LArm:Clone()
            FakeLArm.Parent = PlayerFolder
            FakeLArm.Transparency = S.FakeArmTransparency
            FakeLArm:BreakJoints()

            LArm.Transparency = 1

            local FakeLWeld = Instance.new("Weld")
            FakeLWeld.Part0 = FakeLArm
            FakeLWeld.Part1 = LArm
            FakeLWeld.Parent = FakeLArm

            FakeRArm = RArm:Clone()
            FakeRArm.Parent = PlayerFolder
            FakeRArm.Transparency = S.FakeArmTransparency
            FakeRArm:BreakJoints()

            RArm.Transparency = 1

            local FakeRWeld = Instance.new("Weld")
            FakeRWeld.Part0 = FakeRArm
            FakeRWeld.Part1 = RArm
            FakeRWeld.Parent = FakeRArm

            Instance.new("Humanoid", PlayerFolder)

            for _,Obj in pairs(Character:GetChildren()) do
                if Obj:IsA("CharacterMesh") or Obj:IsA("Shirt") then
                    Obj:Clone().Parent = PlayerFolder
                end
            end
        else
            local ArmTable = CreateArms()
            ArmTable[1].Model.Parent = PlayerFolder
            ArmTable[2].Model.Parent = PlayerFolder

            FakeLArm = ArmTable[1].ArmPart

            LArm.Transparency = 1

            local FakeLWeld = Instance.new("Weld")
            FakeLWeld.Part0 = FakeLArm
            FakeLWeld.Part1 = LArm
            FakeLWeld.Parent = FakeLArm

            FakeRArm = ArmTable[2].ArmPart

            RArm.Transparency = 1

            local FakeRWeld = Instance.new("Weld")
            FakeRWeld.Part0 = FakeRArm
            FakeRWeld.Part1 = RArm
            FakeRWeld.Parent = FakeRArm
        end
        --Extra gun effecting code
    end
end