Overriding Calendar Style in DatePicker

So, I wrote this code some time ago, and it worked fine, but recently, for some reason, now it doesn't work at all. Here xaml ...

<DatePicker SelectedDate="{Binding Criteria}" IsEnabled="{Binding IsEnabled}" Width="130" HorizontalAlignment="Right">
    <DatePicker.CommandBindings>
        <CommandBinding Command="controls:DateCommands.SelectToday" CanExecute="CommandBinding_CanExecute" Executed="CommandBinding_Executed"/>
    </DatePicker.CommandBindings>
    <DatePicker.CalendarStyle>
        <Style TargetType="{x:Type Calendar}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Calendar}">
                        <TabControl>
                            <TabItem Header="Calender">
                                <CalendarItem Background="{TemplateBinding Control.Background}" BorderBrush="{TemplateBinding Control.BorderBrush}" BorderThickness="{TemplateBinding Control.BorderThickness}" Style="{TemplateBinding Calendar.CalendarItemStyle}" />
                            </TabItem>
                            <TabItem Header="Relative Time">
                                <Grid>
                                    <Grid.ColumnDefinitions>
                                        <ColumnDefinition/>
                                        <ColumnDefinition/>
                                    </Grid.ColumnDefinitions>
                                    <Button Grid.Column="0" Command="controls:DateCommands.SelectToday" CommandParameter="Today" Content="Today" />
                                    <Button Grid.Column="1" Command="controls:DateCommands.SelectToday" CommandParameter="Yesterday" Content="Yesterday" />
                                </Grid>
                            </TabItem>
                        </TabControl>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </DatePicker.CalendarStyle>
</DatePicker>

Basically, I redefine the date picker calendar and place a tab control that allows the user to select the relative time macro rather than the actual time (as a result of which the generated query always uses this relative time). This works well, but now when I try to select from the calendar, nothing happens and no values ​​are ever populated in the field or in the backup property.

I took out the code and dumped it into a new project to experiment and could not get this simple case to even work ...

<DatePicker Width="130" HorizontalAlignment="Right">
    <DatePicker.CalendarStyle>
        <Style TargetType="{x:Type Calendar}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Calendar}">
                        <CalendarItem Background="{TemplateBinding Control.Background}" BorderBrush="{TemplateBinding Control.BorderBrush}" BorderThickness="{TemplateBinding Control.BorderThickness}" Style="{TemplateBinding Calendar.CalendarItemStyle}" />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </DatePicker.CalendarStyle>
</DatePicker>

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