Thank you for writing back.
According to the provided screenshot, it seems that you were missing parameterless constructor for your custom shapes. Indeed, creating such a constructor is the appropriate solution in this case. As a side note, you can refer to the following help article where you can find the relevant events when serializing/deserializing shapes: http://docs.telerik.com/devtools/winforms/diagram/events/diagram-events
I hope this information helps. If you have any additional questions, please let me know.