It is not clear what you are doing or what the problem is, but it sounds like maybe the contents of whatever container you are checking the position of are what is moving, not the container itself.
Picture a bit of type. Picture that I do not want it to move, and according to the numerical values of it's X Y position, it should not move.
when I play this animation in Flash, this bit of type moves just a little bit at one point. I can find no numerical reason of why it moves. but it does move.
in the SWF, it does not move.