Scribus / OSX / QT 5.1+ destroys its own menus when our plugins load

Scribus uses its own menu management system to build menu structure, but bases this on standard Qt classes. Scribus loads and builds its menus, and then plugins are loaded. Plugins that need menu items request to be added to the menu and get menu items. In Qt 4.x and 5.0, these menus all build correctly and work properly. In 5.1 and 5.1.1RC, when the plugin menu items are created, the menu items in the main menus turn into normal menu items, and lose their submenu items.

Eg, menu structure with plugins
without plugins in Qt 5.1, or Qt 5.0: Item / Duplicate & Transform / has three submenu items
with 1 single plugin being added to the Item menu at the bottom, even the Duplicate & Transform submenu and its items simply turn into a menu item called Duplicate & Transform that does nothing.

I am attaching a screenshot of our Item menu. The smooth path plugin is loading itself into the Path Tools menu. In one, you can see the Duplicate/Transform menu item has changed from a submenu to a basic menu item. No code changes are required to create this, just build with Qt5.1 vs 5.0.

thanks
Craig