I have investigated the described scenario and also managed to reproduce it on my end. With the current implementation of the widget, the scenario where dragging an event that is grouped by multiple resources has not been designed to automatically re-position the event for all of the resource. Instead, the event resource is set to the corresponding drop target resource.
You are also correct that this behavior can be improved to automatically re-position the event for all resources, which will also be more intuitive for the users. Therefore, I have logged this as a new feature request on your behalf in the Telerik UI for ASP.NET MVC Feedback Portal where the rest of the community will be able to discuss and vote for this feature:
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