This happens because when the user drops the mouse there is code that is supposed to execute which repaints the RadWindow. If it is already closed, it will be shown but the needed handlers will not be attached.
To avoid this, you have two options:
- disable the Move and Resize behaviors (either from the markup, or dynamically, when the update/insert is initiated)
- use the control's events to check if it is already closed when dragging/resizing ends and hide its popup if so. I am attaching a simple example of this approach here.
I hope this explains the case.
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