Xamarin Community Toolkit LongpressCommand stops item selection in CollectionView iOS

Question

The code works as expected in Android but in iOS works inconsistently. The selected label's border changes colour when tapped, sometimes. After 3 or four taps of different labels they cease to be selected at all. Long pressing a label works as expected, opening a different view. On returning to the view containing the CollectionView code attached, label selection has been re-enabled. The process then repeats itself. I've tried changing Nuget versions of both Xamarin.Forms and Xamarin.Community.Toolkit(even the latest pre-release), xaml and code-behind to no avail. I'm at a loss. Any help would be appreciated.

<CollectionView x:Name="categoryCollectionView"
                                ItemsSource="{Binding Categories,Mode=TwoWay}"
                                SelectionMode="Single"
                                SelectedItem="{Binding Category}"
                                SelectionChanged="OnMenuItemSelected"
                                Grid.Column="0"
                                HorizontalOptions="FillAndExpand"
                                Grid.ColumnSpan="8" 
                                Grid.Row="3"
                                VerticalScrollBarVisibility="Always" >
                <CollectionView.ItemsLayout>
                    <GridItemsLayout x:Name="CategoriesGridLayout"
                                     Orientation="Vertical" 
                                     Span="3"
                                     VerticalItemSpacing="2"/>
                </CollectionView.ItemsLayout>
                <CollectionView.ItemTemplate>
                    <DataTemplate>
                        <Grid  Padding="0">

                            <VisualStateManager.VisualStateGroups>
                                <VisualStateGroup x:Name="CommonStates">
                                    <VisualState x:Name="Normal" />
                                    <VisualState x:Name="Selected">
                                        <VisualState.Setters>
                                            <Setter TargetName="lblCategory" Property="Label.TextColor" Value="Red" />
                                            <Setter Property="BackgroundColor" Value="Green" />
                                        </VisualState.Setters>
                                    </VisualState>
                                </VisualStateGroup>
                            </VisualStateManager.VisualStateGroups>

                            <StackLayout  Orientation="Vertical" 
                                          VerticalOptions="Center"
xct:TouchEffect.LongPressCommand="{Binding LongPressCategoryCommand, Source={RelativeSource AncestorType={x:Type vm:CategoryVM}}}"
                                          xct:TouchEffect.LongPressCommandParameter="{Binding CategoryString}" >
                                <StackLayout.Margin>
                                    <OnPlatform x:TypeArguments="Thickness" iOS="2,2,4,4" Android="2" />
                                </StackLayout.Margin>

                                <Label  x:Name="lblCategory"
                                        Text="{Binding CategoryString}"
                                        FontSize="Small"
                                        BackgroundColor="#f5e2e1"
                                        VerticalOptions="Center"
                                        HorizontalOptions="CenterAndExpand"
                                        WidthRequest="350"
                                        Padding="5"
                                        TextColor="#232F34"
                                        LineBreakMode="TailTruncation"
                                        Style="{DynamicResource CategoryLabelStyle}" >
                                    <Label.Triggers>
                                        <DataTrigger TargetType="Label"
                                                         Binding="{Binding Source={x:Reference fontSizeSwitch}, Path=IsToggled}"
                                                         Value="true">
                                            <Setter Property="FontSize"
                                                          Value="Medium" />
                                            <Setter Property="Padding"
                                                          Value="2" />
                                        </DataTrigger>
                                    </Label.Triggers>
                                </Label>

                            </StackLayout>
                        </Grid>
                    </DataTemplate>
                </CollectionView.ItemTemplate>
            </CollectionView>