Problem with stage and all of it's objects moving

Hi Everyone

Not sure if anyone else has had this problem before but I hope I’m not the first!

What I did:
I created a bunch of movie files that can be selected by the user. The user can then drag and drop it on rectangular movie and if it’s released within this movie, it is effectively added to the basket.

My problem:
When the movie has been added to the basket, for some reason everything that is on the stage (whether they are movieclips, buttons, simple rectangles with no instances, EVERYTHING) shuffles to the right by around 10 px.

I’ve got no clue how or why this happens, but it only happens the first time an object has been added to the basket.

Has anyone else come across this before? If you have please help!