If a custom cursor (Qt::ForbiddenCursor) is set and when a pop up context menu is shown Custom cursor goes away with mouse move. It can be re-obtained by moving the mouse out of and back into the application or clicking its header. 

Attached example shows this, it is little tricky to reproduce. You will have to move the mouse(cursor) on the edge of context popup and move away from it. Attached is screen recording which shows it.