Super.property -= not working

Whoops this seems to have been posted right before me.

The answer is located here:
Answer to Super vs Public/Private/Protected properties

Thanks to Ayumilove for going out of her way to find this out.
And to lordofduct for breaking down the reason+answer for it!

For some reason when I try and modify parent properties through a child with the
-=
+=
*=
etc
commands, it doesn’t work, it in fact gives an error:

//1086: Syntax error: expecting semicolon before minusassign.
//in relation to:
super._health -= 2;

and also this error TWICE for just the single line of code above:

5000: The class 'com.beastiary.orks.OrkSentry' must subclass 'flash.display.MovieClip' since it is linked to a library symbol of that type.

Which makes NO SENSE since OrkSentry class extends from the Ork class. And the Ork class extends from the MovieClip class. That’s how you’re supposed to use inheritance right? And yes I am importing MovieClip class for each class.

In reference back to the line of code that comes back erroneous:

super._health = super._health - 2;

Works just fine. But I don’t want to write my code like that. I don’t think anyone likes to write code like that.

So anyone run into this problem and can help?