MessageBox automatically closes

### Description

I've encountered an issue where setting the MessageBox title to "Caption" causes the message box to automatically close after being displayed for a few seconds. Why does this happen? I'm currently using .NET 5.

### Reproduction Steps

```C#
private void Button_Click(object sender, RoutedEventArgs e)
{
MessageBox.Show("MessageBoxText", "Caption");
}
```

### Expected behavior

Normally, the MessageBox should only close when I click the close button or the OK button.

### Actual behavior

Actually, when the title is set to "Caption", the MessageBox will automatically close after being displayed for a few seconds.

### Regression?

_No response_

### Known Workarounds

_No response_

### Impact

_No response_

### Configuration

_No response_

### Other information

_No response_