I looked through your project and I noticed that you defined a DataTemplate with a RadGridView in it. You are using it as a CellTemplate for the main GridView's columns. Thus, you have a RadGridView in each cell of the main RadGridView, am I right? Judging from the attached picture, you have a few cells, which have a multi-line content. If i am right, these should be separate GridViews with multiple rows. However, there are neither vertical, nor horizontal lines. Moreover, the root border of RadGridView's template is not visible, which implies that you have a custom ControlTemplate, which I cannot find in the XAML that you have sent to us. Is this issue reproducible with the default styles? Additionally, can you please confirm whether the entire rows are disabled, propagating IsEnabled=false to their child controls, or only the RadGridViews are disabled. Generally, it will be great if you can send us a sample dummy project that illustrates this problem, as this looks like a heavily-customized scenario.
As a side note, I would like to mentiоn that this looks like a quite encumbered layout, with a very deep visual tree (which is slow, not only for initial parsing, but for propagating of layout changes at runtime). Have you considered replacing the nested RadGridViews, with simpler controls (i.e. System.Windows.Controls.ItemsControl)?
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