I believe you custom style for RadComboBox does not get applied in the right time. If you render a RadComboBox and only then merge resources in your application resources, the RadComboBox will not pick up its style because it does not support dynamic theme switch. Instead, it will keep its default look. It will apply its new style only after the layout has been redrawn, i.e. refreshed. Which is why is picks up the style the second time. I suggest you try mergind resources on the application level before your layout in the dialog is rendered.
the Telerik team
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