I have exactly the same problem.
I have a ribbon control and a data grid in my window. If I select a cell in the data grid and then press a ribbon button. The original source property is then set to the selected cell in the data grid. When I press the ribbon button before I select a cell,
the original source property is set to the button.
From my understanding of RoutedEvents, this shouldn't be possible, because the ribbon control and data grid are not on the same path of the visual tree!
Has anybody a solution for this problem?
Any help will be appreciated.