shapetweening can give really unpredictable result when you're not using really basic shapes.
You can do 3 things here:
1 - Use shape hints
2 - Tween your shapes on different layers, so it is less complex on one layer
3 - Animate frame by frame, more work but maximum control
thanks but i have tried those the thing im trying to avoid is having to go back into each frame and remove the random lines XD