Unless I've badly misunderstood how the mask works, something is quite wrong here.
Layer 1 - a picture of an old TV.
Layer 2 - a TV snow animation.
Layer 3 - a Flash text.
I created a PNG mask with the screen area cut out so I can put stuff on the screen and only the screen. Works great so far. In Layer 2 and 3 this mask is applied to the Layer.
However, I had to scale the Flash text to fit in the screen area. As soon as I mess with the clip properties for the SWF, to scale and reposition, the mask is scaled and moved with it! Same happens with the snow MOV file - playing with clip properties affects the layer mask.
Surely this is not working as intended? The layer mask should stay put!
Maybe someone can clear this up or confirm it's a bug.