Hello,
We investigated the scenario and as it turns out the validation border remains visible when displayed in the AdornerDecorator of the ScrollContentPresenter element inside the RadGridView ScrollViewer.
To avoid this, you can extract the ControlTemplate of the GridViewRow element for the theme that you are using and add an AdornerDecorator element to it. The example project attached here shows how this can be done for the Fluent theme.
Of course, feel free to reach out via a new support ticket/forum thread, if you have any further questions regarding this scenario.
Regards,
Vladimir Stoyanov
Progress Telerik
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