A NullReferenceException may occur during the DataGrid cell measure phase. The issue appears to happen when the cells are being generated or prepared for layout:

at Telerik.Maui.Controls.DataGrid.CellsController`1.GenerateCellsForRow(IItemInfoNode rowModel, Int32 rowSlot)
at Telerik.Maui.Controls.DataGrid.NodePool`2.GenerateModelsForInfos(IList`1 itemInfos, ModelGenerationContext modelGenerationContext, MeasureContext measureContext)
at Telerik.Maui.Controls.DataGrid.NodePool`2.MeasureForward(MeasureContext& context)
at Telerik.Maui.Controls.DataGrid.GridModel.MeasureCells(RadSize availableSize)
at Telerik.Maui.Controls.DataGrid.DataGridContentLayout.MeasureChildren(Double widthConstraint, Double heightConstraint)
at Microsoft.Maui.Platform.MauiPanel.MeasureOverride(Size availableSize)
at ABI.Microsoft.UI.Xaml.IFrameworkElementOverrides.Do_Abi_MeasureOverride_0(IntPtr thisPtr, Size availableSize, Size* result)