You should set SelectedValuePath
to Content
:
<ComboBox Grid.Column="1" Grid.Row="9" SelectedValue="{Binding SelectedReason}"
SelectedValuePath="Content">
<ComboBoxItem Content="Bug Report" IsSelected="True"/>
<ComboBoxItem Content="Suggestion"/>
<ComboBoxItem Content="Complaint"/>
<ComboBoxItem Content="Other"/>
</ComboBox>