Scale9 ignored when MovieClip used as mask

I've got a generic rounded-corner square with scale9 guides applied through the GUI, that I use all over the place in the movie in alot of different sizes.
I'm having an issue with one instance where I use actionscript to set the instance of this square as a mask. When the instance is set as a mask, the scale9 guides are ignored.

I can always just make multiple individual masks already set to size, but it would be nice if I didn't have to, maybe I'm doing somthing wrong.

In the GUI,
I place the instance of the square on the stage,
resize the square to the size I want it.
Then with actionscript I use the following to setup the masking.


No other instances of the square are giving me any problems with the scale9.

The instance being used as a mask, is also contained within another movieclip that has a mask applied to it.
I seem to be finding issues with a few things when multiple levels of masking are applied.

Seems that scale9 is ignored when a horizontal flip is applied as well.

can you link me to your fla file?

Ended up just working around it by using the individual sizes when masking is a factor.
It's really not that much more work or filesize since they're basic vector shapes.