Why is my Body Velocity glitching back and forth? Please help!

Hello!

I need help with a body velocity being glitchy, here's an example video (Along with the code used)

Video:

https://gyazo.com/7b581060c21116699b0d7a33f1bbd577

Code:

local function addKnockback(root,vel,lifeTime,friendly)
    local kb = Instance.new("BodyVelocity",root)

    if not friendly then -- friendly means that if it is not the target, it will give a different name, not really important.
        kb.Name = "KnockbackBV"
    else
        kb.Name = "PushBV"
    end

    kb.MaxForce = Vector3.new(math.huge,0,math.huge) -- Setting Body Velocity's Max Force to math.huge
    kb.Velocity = vel -- this is just setting the velocity of the body velocity.

    game.Debris:AddItem(kb,lifeTime) -- We need to destroy the force so it doesn't go on forever
end

I tried to make this as detailed as I could, please let me know if you need more details!