Content Control in word 2016

Question

I am using content controls in word. In my document I have 3 richtextbox content controls with same title and tag name. In that 2 are already added and one is added for me with below code.

Control = contentControls.Add(WdContentControlType.wdContentControlRichText, selectionRange);

Control.Title = contentcontrol.Title;

Control.Tag = contentcontrol.Tag;

Control.Range.Text = contentcontrol.Range.Text;

The problem is If I chnage the value for richtextbox from document, only 2 are updating value but richtextbox inserted by me is not updating the value in document.

Can anybody solve this issue?