Bug 327964 EPartService's hidePart may fail when trying to hide a shared part that's in a shared container
The placeholder retrieval code in the EPartService implementation doesn't go far down deep enough and actually stops at the shared container level. This causes the placeholder of the shared part to not be found.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
return ((MContext) element).getContext();
		} else if (element instanceof MElementContainer<?>) {
			Object selectedElement = ((MElementContainer<?>) element).getSelectedElement();
			if (selectedElement instanceof MContext) {
				return ((MContext) selectedElement).getContext();
			} else if (selectedElement instanceof MElementContainer<?>) {
				return getSubContext((MUIElement) selectedElement);
			}
		}
		return null;
	}
	private void internalFixContext(MPart part, MUIElement oldSelectedElement) {
		if (oldSelectedElement == null) {
			return;
		}
		MContext parentPart = getParentWithContext(oldSelectedElement);
		if (parentPart == null) {
			
			return;
		}
		IEclipseContext parentContext = parentPart.getContext();
		IEclipseContext oldContext = getSubContext(oldSelectedElement);
		Object child = parentContext.getActiveChild();
		if (child == null || oldContext == null || child == oldContext) {
			if (part == null) {
				
				IEclipseContext currentActive = parentContext.getActiveChild();
				if (currentActive != null)
					currentActive.deactivate();
			} else