Tree model update

Hi I got an UI5 Tree which is bound to a JSON Model,

i need to update the nodes without collapsing the whole tree and keep the position of the scrollbar.

But when I update the model via setData(newData) the whole tree is rerenderer so the scrollbar is on top of the tree.

I am able to change the nodes direct via tree.getNodes()[0].setProperty... which leads to rerendering of exactly the node that I changed.

But that does not change the model...

So what is the correct way to update the model?

Thanks in advance,

Juri Zeisler