How to reproduce: check the attached project: Workaround: when the form is opened in the designer make sure that all pages are made visible at least ones so the controls are initialized, before attempting to access collection editors via properties window
The current behavior of the page view is desired and by design. The original issue is caused by an error inside the grid and it is resolved by the linked item: RadGridView: NullReferenceException when opening the Relation Collection Editor and the Site of the master template is null (telerik.com).
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