Flash cs4 3d rotation messing positioning

i make a snaphot of an image (with bitmapData.draw), then copy individual parts, and place that image below the current one.

i want to flip parts of an image with rotationY to reveal to bottom image.

so i need to pre-apply rotationY to 180 to bottom parts before i flip them so when they “turn around” their rotation is 0.

Everything is fine with positining when i dont apply any rotation, but when i do, bottom parts are not positioned correctly.

look at the picture, at the bottom you can see almost 2 px orange line (whic is actually a bottom picture peaking from beneath).
it should be like that , it should be straight below the top one (like it is when i dont apply rotation)

it really anoying… and i dont know why is this hapenning…

ofcourse if i trace positions of top and bottom parts everything seems fine, but obviously its not…