Using a grid with grouping and selection is totally broken

I created a very simple Plunker to show the problems: http://plnkr.co/edit/zCstBVfGphTmyXJOYP7h?p=preview This bug occurs in the latest version, as of today, 4.4.11. There are a few issues:

1. Select all doesn't select the group headers and vise versa.
2. Selecting a group header and then deselecting one of the selected children doesn't deselect the group header itself.
3. Selecting a few (not all) children under a single group header and then selecting the group header of those children changes all the selected children to deselected and all the deselected children to selected.