Lightning Not Directly Hitting Target?

Hello, I recently made a lightning script with this tutorial: https://www.youtube.com/watch?v=GqGXzQEio98

The problem is that the lightning doesn't directly hit the target it's aiming for, it either goes through the target or doesn't reach the target. Example:

https://gyazo.com/40a8465c919d6a67071eeaea9e2c1b29

Is there any better methods of making lightning besides this? Like I want more of a zig zag pattern instead of the lightning slightly bending.

Here's the script I used to make it. Any help is appreciated

a = script.Parent
b = workspace.b
storage = Instance.new('Folder',workspace)
storage.Name = 'beamstorage'
beam = Instance.new('Part')
beam.Anchored = true 
beam.CanCollide = true
beam.Size = Vector3.new(.2,.2,0)
beam.BrickColor = BrickColor.new('Bright blue')
beam.Material = 'Neon'
amount = 20
pos = a.Position
pos2 = b.Position
mag = (pos - pos2).magnitude
offset = 0
off = Vector3.new(math.random(-offset,offset),math.random(-offset,offset),math.random(-offset,offset))
last = pos 

for i = 0,mag,amount do 
    local pos = last 
    local pos2 = pos + -(pos-pos2).unit*amount+off
    local beamclone = beam:Clone()
    beamclone.Parent = storage
    beamclone.Size = Vector3.new(beam.Size.X,beam.Size.Y,(pos-pos2).magnitude)
    beamclone.CFrame = CFrame.new(pos:Lerp(pos2,0.5),pos2)
    last = pos2
    if i == amount then
        beamclone.BrickColor = BrickColor.Red()
        beamclone.Size = Vector3.new(0,0,(beamclone.Position - b.Position).magnitude)
    end
end