If this works for your particular case you can indeed override the hiding of the iframes. However, there are still scenarios (e.g a modal window in a restriction zone) when if the user makes an invalid drag and goes over an iframe, the issue will occur and we want also to keep backwards compatibility. That is why we do not plan to change this behavior internally in case of modality. We could, however, consider implementing a server property (whose default value will keep the current behavior) to control this in the future, depending on customers feedback.
Thank you for your feedback, we appreciate it and we will be glad to receive it in future, too!
All the best,
the Telerik team
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