Can't update position with SetPositionInViewport when enable global invalidation

When GlobalInvalidation is enabled, do not update to the position set by SetPositionInViewport. It works fine when GlobalInvalidation is disabled.

1. Create a new widget to display the Image.

2. Connect CreateWidget and AddToViewport node to BeginPlay in level blueprint.

3. Convert the location of an actor on level with ProjectWorldToScreen.

4. Set the converted Screen Position with SetPositionInViewport to the position of the widget.

5. Connect step3 and step4 to EventTick in level blueprint.

6. launch game with Standalone.

7. Exec "Slate.EnableGlobalInvalidation 1".

Result:

 Not update position of widget.

Expected:

Update position of widget by SetPositonInViewport. 

The widget moves to the same screen position as the actor, just like the lockon marker.