Stackview Push and Pop destroys and creates a new page

Gunkut

Hello, I have many pages and when a button is clicked I make transitions between these pages with a StackView, push and pop. And in these pages when corresponding buttons are clicked I make these buttons red. However, when I pop and re-opened the same page with a push, button is no longer red. So that makes me think that pop and push destroys and creates a new page which is the opposite what is written in docs: This means that any item pushed onto a StackView will never be destroyed by the StackView; only items that StackView creates from Components or URLs are destroyed by the StackView.

Here is the code for stackview:

Window{
   id:main
   property bool isAbsOffRoad: false
   StackView{
      id:contentFrame
      initialItem:Qt.resolvedUrl("qrc:/MainPage.qml")
      Connections{
         target:contentFrame.currentItem
         onBackButtonPressed:{
            contentFrame.pop() }
         }}

And then here is how I push:

Item {
   id:backgroundItem
   LeftButtons{
      id:buttonSettings
      MultiPointTouchArea{
         onPressed{
            contentFrame.push("qrc:/SettingsPage.qml")}
}}

I cannot see a reason why the page doesn't preserves it's state when popped and pushed back. What might be the reason?

Another question is: I get a QML Connections: Cannot assign to non-existent property "onBackButtonPressed". However, back buttons work. Why I get that error?
Kind regards.