If you try to dynamically set the ForbiddenZones
property to a zone where the dock is currently docked, you will get this behavior (another "dock target space" appears in the zone). In general the dock needs to be out of the zone (not docked to it) when you are setting it as a forbidden, otherwise you will get undefined behavior.
Can you please explain in detail what exactly you want to achieve, and we will be glad to help you?
the Telerik team