At least in Windows, in a QTreeView enabling extended selection, if you select two items, one having its "drag enabled" flag set and the other one not, you can drag both of them around the view. After drop, the item with the flag unset will disappear.

Run the attached application to reproduce the bug:

In the view, "NewFilter" can't be moved and all other items can. If you select "NewFilter" and one of its children (i.e. "Folder_Component_1") and drop them above "Component", "Folder_Component_1" is put above "Component" and "NewFilter" disappears (as well as "Folder_Component_2").