I'm getting this same stack trace for UI for Windows Phone 8 Q2 2015 (using Telerik_UI_for_WindowsPhone8_2015_2_0624_DEV_hotfix). I've moved the design folder as stated but anytime I select XAML code related to a Telerik Chart the designer throws the stack trace.
Are there any other workarounds?
On a seemingly unrelated but maybe relevant topic. Whenever I start up VS on a new day I get a message stating that there is a new version of Telerik UI for Windows Phone 8 Q2 2015 (0624). I've downloaded it and copied the directories over my existing installation but the message still arrives each day. What is the procedure for upgrading with the hotfixes? Do you have any links to the procedure? I'm only asking because perhaps this stack trace issue has been fixed but I've applied the hotfix incorrectly.