Ok I think I see what you’re doing now. You have movieclips that have code and variables in them. These movieclips are being added to frames in the main timeline.
Yes that would cause a problem. What happens is every time you hit a keyframe where that moveclip “appears”, it would call its constructor and probably wipe out your saved variables.
I again revert back to my previous post in recommending that no code exists on frames. I also recommend not manually adding objects to your stage. If you force yourself to set your stage up using code, you then force yourself to properly handle constructors and what-not.
_global variables is a dangerous road to go down and can lead to debugging hell if done incorrectly. You’ll be stronger in the long-run if you just stick to proper Object-Oriented-Programming principles.