Hello,
we use a FlexyGantt with special lines (as in the DynamicSpecialLines sample) in a TabControl.
If you scroll through the gantt, the special lines will be updated normally but after the tab is changed and changed back to the tab with the gantt, the updated does not work anymore.

This is easily reproducible by adding a TabControl to the DynamicSpecialLines sample and place the Gantt in one TabItem and add another empty TabItem.
<TabControl>
<TabItem Header="Tab with Gantt">
<gantt:GanttControl x:Name="ganttControl" Grid.Row="1" />
<!-- FlexyGantt has the same problem -->
<!--<fxgantt:FlexyGantt x:Name="ganttControl"
Grid.Row="1"
TaskStartTimeBinding="{Binding StartTime}"
TaskEndTimeBinding="{Binding EndTime}" />-->
</TabItem>
<TabItem Header="Empty tab" />
</TabControl>
Best regards