Shape tweening problem!

Its really annoying. im just tryin to make a lazer shoot round the page making a square shape. its jkust one stroked line with a shape tween on but it flips the line round the wrong way even though im only moving one end. really annoying the first edge tweens fine but the 2 and 4th ones mess up.

check the fla. to see what i mean.

iv taken the tween out cos it was makin the fla bigger. but just add a shape tween between the frames and ull see what i mean.

how do i stop it flipping!!!?

cheeeeeers