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
part.setLabel(descriptor.getLabel());
		part.setIconURI(descriptor.getIconURI());
		part.setTooltip(descriptor.getTooltip());
		part.getHandlers().addAll(EcoreUtil.copyAll(descriptor.getHandlers()));
		part.getTags().addAll(descriptor.getTags());
		part.getBindingContexts().addAll(descriptor.getBindingContexts());
		return part;
	}
	public MPart createPart(String id) {
		MPartDescriptor descriptor = findDescriptor(id);
		return createPart(descriptor);
	}
	public MPlaceholder createSharedPart(String id) {
		return createSharedPart(id, false);
	}
	public MPlaceholder createSharedPart(String id, boolean force) {
		MWindow sharedWindow = getWindow();
		
		MPart sharedPart = null;
		
		if (!force) {
			for (MUIElement element : sharedWindow.getSharedElements()) {
				if (element.getElementId().equals(id)) {
					sharedPart = (MPart) element;
					break;
				}
			}
		}
		if (sharedPart == null) {
			MPartDescriptor descriptor = findDescriptor(id);