My walk script sometimes stops the humanoid for some reason?

So, I'm making an RPG game, and my enemies sometimes break. They don't move at all! There are no errors or anything, they just stop working.

There's a few other things in my code, like the exp on death and stuff, but here's the loop:

while true do
    local low = script.Parent.Detect.Value
    local plr = nil

    --check distances
    for _, player in pairs(game.Players:GetPlayers()) do
        dis = player:DistanceFromCharacter(script.Parent.Head.Position)
        if dis <= low then
            plr = player
            low = dis --as soon as I added this line the code started breaking
        end
    end

    wait(.01)
    -- if there is a player in range, move to it
    if plr and plr.Character then
        repeat

            if plr.Character:FindFirstChild("HumanoidRootPart") then move(plr.Character.HumanoidRootPart) end
            if plr.Character.Head.Position.Y >= script.Parent.Head.Position.Y + 1 then script.Parent.Humanoid.Jump = true end
                wait(.01)
        until plr:DistanceFromCharacter(script.Parent.Head.Position) >= script.Parent.Detect.Value or not plr.Character:FindFirstChild("HumanoidRootPart")
        if plr.Character:FindFirstChild("HumanoidRootPart") then move(plr.Character.HumanoidRootPart) end
    end
end

Oh, and I should probably add the move function here too:

function move(part)
    if part then
        local to = part.Position
        local p = part.Parent[part.Name]
        script.Parent.Humanoid:MoveTo(to,p)
    end
end

please help