BarIndicator is not updated when using GaugeRanges and their Min and Max properties are changed at runtime. The indicator's layout is updated only when the gauge control is re-sized.

Possible workaround:

Update measure and arrange the  BarIndicator control manually. 

        var size = this.BarIndicatorRanges1.RenderSize;
        this.BarIndicatorRanges1.Measure(Size.Empty);
        this.BarIndicatorRanges1.Measure(size);
 
        this.BarIndicatorRanges1.Arrange(new Rect(size));
        this.BarIndicatorRanges1.UpdateLayout();