Thank you for the patience,
Query 1: We would like to let you know that in RadialSlider Value property is working as expected. We have changed the radial slider value by using the TextBox's textchanged event and there is no need to call any update or refresh method.
Query 2: We would like to let you know that the radial slider responds to the mouse click only when its parent form contains the focus and when the OpenFileDialog opens, radial slider does not catch the mouse click.
We have prepared a sample for your requirement and it is available in the following location. Please look into the sample and confirm us whether this is your requirement or could you please modify in this sample to reproduce the issue.
Please let us know if you need any further assistance .