Dragging not working highcharts in 4.1.8

I am sure this is the same issue already noted but I am unable to drag a data point in highcharts v 4.1.8 if 2 series are overlapping each other. Our use case is that we have a baseline series with dragging disabled and current series that sits on top and should be draggable. When hovering over data points it is the baseline (bottom series) data point that gets selected rather than the top series (as per v4.1.2)? As the bottom series has dragging disabled we cannot change the required data point. Any ideas on how to solve this?