On some rare cases, RadPane.OnPaneLoaded is being called before ApplyTemplate was called, and therefore, UpdateAllowDrag which tries to find the first child of the rad pane (the "wrapper" grid) fails, and pane remains undraggable.

To reproduce this issue, I have a button that when clicking on it, it adds a new pane (There is a collection of View Models, that when items are added or removed, then a code that is using binding to that collection adds or removes a pane.

The scenario happens when the system is laggy (For example, heavy UI on the panes content), and I'm adding several view models to that collection.
It doesn't always happen, but sometimes, one of more of the panes are not draggable.
I can clearly see that the OnPaneLoaded was called before the OnApplyTemplate was.

Maybe it can be a good idea to call UpdateAllowDrag on the OnApplyTemplate function if the OnLoad was called first.