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.getContext().activate();
		}
	}
	public MPart findPart(String id) {
		MApplicationElement element = modelService.find(id, getContainer());
		if (element instanceof MPlaceholder) {
			((MPlaceholder) element).getRef().setCurSharedRef((MPlaceholder) element);
			element = ((MPlaceholder) element).getRef();
		}
		return element instanceof MPart ? (MPart) element : null;
	}
	public Collection<MPart> getParts() {
		return modelService.findElements(getContainer(), null, MPart.class, null);
	}
	public boolean isPartVisible(MPart part) {
		if (isInContainer(part)) {
			MUIElement element = part;
			MElementContainer<?> parent = part.getParent();
			if (parent == null) {
				
				element = part.getCurSharedRef();
				if (element == null) {
					return false;
				}
				parent = element.getParent();
				if (parent == null) {
					return false;
				}
			}
			if (parent instanceof MPartStack) {