It always breaks on the third line and I no idea why it does it, I don't know if there is something wrong with Until or the equal signs. If you wonder what this script is, its a floating script.
w = 0
while wait() do
repeat until W == 20
script.Parent.Position = script.Parent.Position + Vector3.new(0, 0.1, 0)
W = W + 1
print(W)
repeat until W == 60
script.Parent.Position = script.Parent.Position + Vector3.new(0, 0.01, 0)
W = W + 1
print(W)
repeat until W == 40
script.Parent.Position = script.Parent.Position + Vector3.new(0, -0.01, 0)
W = W - 1
print(W)
repeat until W == 20
script.Parent.Position = script.Parent.Position + Vector3.new(0, -0.1, 0)
W = W - 1
print(W)
repeat until W == 0
script.Parent.Position = script.Parent.Position + Vector3.new(0, 0.01, 0)
W = W - 1
print(W)
end

1 comment
You are repeating nothing, so do repeat wait() until