Regression in 5.9.2: Internal dragging in QTableView inside QDialog freezes the dialog

I've encountered a bug which is present in 5.9.2 but not 5.9.1.  Specifically, this is related to setting up a QTableView which has a setDragDropMode of InternalMove.  If I add such a widget to a QMainWindow directly, it works fine – if you click and drag inside the QTableView, borders get updated properly and all is well.

If I add the widget inside a QDialog, however, pretty much the instant my mouse starts to move initially, the entire dialog totally freezes up, my mouse pointer remains the mid-dragging status, and the only way to return control to the dialog (that I've found, anyway) is to hit Escape (which also cancels the drag).

I've got a full app which is exhibiting this behavior, but I'm also attaching a simple pyqt example which should be pretty well stripped down to the essentials (apologies it's not C++!)