WPF Application (.Net Framework 4.8): Keyboard delay in DataGrid when surrounding Border has a shadow.

_This issue has been moved from [a ticket on Developer Community](https://developercommunity.visualstudio.com/t/WPF-Application-Net-Framework-48:-Ke/1362581)._

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[severity:It's more difficult to complete my work]
My DataGrid contains 32 rows with 32 check boxes. The DataGrid is the child of a border with a shadow.
When I click a check box and hit a cursor key (e.g. Up), then my application hangs for 10 seconds (Depending on number of check box columns).
When I remove the shadow, everything's ok.

XAML:
```

... 30 more check box columns

```

Code Behind:

```
InitializeComponent();
testDataGrid.ItemsSource = new bool[32]; // Any array to create rows
```

[CheckboxColumnTest.zip](https://aka.ms/dc/file?name=B6508572ff87f4ffe9283a70e9328df69637508786763633100_CheckboxColumnTest.zip&tid=6508572ff87f4ffe9283a70e9328df69637508786763633100)

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### Original Comments

#### Feedback Bot on 3/9/2021, 07:11 PM:

We have directed your feedback to the appropriate engineering team for further evaluation. The team will review the feedback and notify you about the next steps.

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### Original Solutions
(no solutions)