Can you make sure that the RibbonView project reference the binaries at the same place where the Core_WPF.sln output them, so it's not using different version of Telerik.Windows.Controls. (Same for Navigation and Input).
If all the binaries are built and correctly referenced, there shouldn't be any issues. Still you can remove the Design projects if they cause you troubles.
Hope this helps.
the Telerik team
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