Brushchart doesn't show all dates

I am trying to use the custom visual called Brush Chart. It's a slicer/highlighter for time series. So I have a date column and a corresponding counts column. The date rage in original data is 2002-2016 however in the visual it only shows part of it. Even if I filtered the date to have only a single year, it's still not showing all month of the selected year.

Also, if you look at the detail of the visual, it just doesn't make sense that there are circles out there, which mean two y value for a same x value. 

Anybody knows how to solve this?