Reproducable in the following Dojo:

https://dojo.telerik.com/@foxontherock/UKureVOy/2 

Open the daterangepicker and make a selection, for example 10th of December to 15th of December(10.12 - 15.12). 

Open the daterangepicker and make another selection 12th of December to 17th of December(12.12 - 17.12).

Only the 17th is selected instead of the entire 12-17 range.