I assumed the code you posted was from the component, as it would have been relevant.
When i read:
if (auto_size.toString() == "true")
{Stage.scaleMode = "noScale";}
I then assume that if auto_size is set to something else than "true" the Stage.scaleMode won't be set to "noScale"

You follow?

So, you need to find what (other) action coming from that component would set Stage.scaleMode to "noScale", see if it's possible to disable it.
Maybe via the output (same amo) or via Movie Explorer.

Or, you could post a .fla with only that component in it, so we can check for you.

gparis