Can only select either ONE or ALL nodes at any given level

[yanndubois]

All child nodes of a parent can be selected by selecting the parent, but unable to select fewer than all or more than one child node under a parent. When trying to select more than one child, the checkboxes behave like radio buttons and the last selected child is the only child that is selected. This also happens when attempting to select more than one parent node. Only one parent remains selected at a time.