Yes, you're right, it is working correctly in latest 2018.2.515. I was trying 2017 version.
Posted on:12 Jun 2018 11:04
May I ask you which version of Telerik UI for WPF you are using? I have tested the same scenario with our latest official version - 2018.2.515 and everything is working as expected. Please check the attached video for a reference.