Thanks for the additional information and I understand that you don't have time to create a sample project, but unfortunately without one we could not know what is the logic/implementation of your application.
For example, did you implemented your own DragAndDrop logic or from where you drag the shape - is it from a RadDiagramToolBox
or somewhere else.
Also in one of your previous post you mention you reproduce the issue only on one of the two computer you use. May I ask you to share with us the configuration (OS version, .NET version) of the computer on which you reproduce the described behavior?
Thank you in advance for your cooperation.
the Telerik team