Titanium Alloy SplitWindow IOS strange behavior change width

  <SplitWindow id="home" platform="ios" formFactor="tablet">
            <Require src="master" id="master"/>
            <Require src="detail" id="detail"/>
  </SplitWindow>

I have a strange behavior if I drag horizontally the black separation line between the two windows. The windows change size adapting to my movements.

And, if I change the width of the windows is even easier to identify the black separation line

function demo() {
Alloy.Globals.master.win.width = 512;
Alloy.Globals.detail.win.width = 512;
}

[For test purpose you have to aim the exact pixel of the black separation line ]

Could you tell why is this happening and how do I stop this behavior??