If you make a layer and give it unique zoom y rate, then save and reload your .cap, the zoom y rate will be back to 100%. zoom x rate saves fine though.
This seems true for any number of layers...none save the zoom y.
Also, On my XP system, the Auto mirror feature still does not work in conjunction with the platform behavior. I can force it to work with an event that says change angle to 180, but as soon as it takes effect, the object falls right through the level.